add plugin settings, per-tile refresh, settings menu, touch-friendly UI

- Plugin settings infrastructure in PluginManager with config/plugin_settings.cfg
  storage, manifest [settings] sections, CRUD API, plugin_setting_changed signal
- Per-tile refresh intervals: 100ms base tick, per-tile update_interval_ms
  metadata, dynamic tween durations clamped to refresh window
- Settings menu (PopupPanel) with General/Plugins/About tabs, plugin
  activation toggles, per-plugin settings cog buttons
- Plugin settings popup (PopupPanel) with dynamic UI from setting definitions
  (SpinBox/CheckBox/LineEdit), auto-save on change
- Modal behavior: exclusive = true on settings windows
- Touch-friendly sizing: enlarged close buttons, cog buttons, controls, spacing
- Red corner close button redesign with rounded corners, hover/pressed states
- Split system_monitor into local_system_monitor (CPU, Memory) and test plugins
- Plugin activation/deactivation with layout preservation

AGENTS.md

@@ -24,9 +24,11 @@ V Panel is a Godot Engine project that builds a fancy real-time status monitor.
 - Modules are direct children of the grid (not cells). Visual cells (`PanelContainer`) are shown only during drag as drop-zone guides.
 - Grid data model: each module stores `grid_col`, `grid_row`, `grid_w`, `grid_h` via `set_meta()`. A 2D `_grid[row][col]` array tracks cell occupancy (supports multi-cell spans).
 - `place_module(module, col, row, span_w=1, span_h=1)` — public API for adding modules with optional span.
+- `@export var grid_columns: int` / `@export var grid_rows: int` — fixed grid dimensions. Square cells, centered layout.
 - Drag-and-drop: `_begin_drag` → `_update_drag` → `_end_drag`. Occupancy is cleared during drag and restored on drop. Swaps modules when dropping on occupied cells. Falls back to source position if dropped in grid gap or outside grid bounds (`mouse_exited` safety handler).
 - Resize: `_try_begin_resize` detects clicks within 10px of any module edge. `_update_resize_preview` shows a ghost `ColorRect` at the target span. `_end_resize` commits the new span after overlap check. All 4 edges and corners supported.
-- Double-click: opens `PopupMenu` with shader preset names from `ShaderPresets`. Selection applies all preset params to the module's `ShaderMaterial`.
+- Long-press gesture: 500ms hold, 10px drag threshold. Opens action menu with toolbar (⚙, ℹ, ✕/+) and "Themes ▸" submenu.
+- `_open_settings(menu_panel)` — opens `settings_menu.tscn` as exclusive modal PopupPanel.
 - Grid rebuild (`_rebuild_grid`) preserves module metadata (span data lives on modules). Cells are torn down and rebuilt on column/row changes. Orphaned popups cleaned up during rebuild.
 
 ### Shaders
@@ -63,20 +65,33 @@ V Panel is a Godot Engine project that builds a fancy real-time status monitor.
 
 ### Plugin System
 - `autoload/plugin_manager.gd` — autoload singleton, scans `res://plugins/*/plugin.cfg` at startup.
-- Each plugin folder contains a `plugin.cfg` INI file with `[plugin]` metadata and `[tile_N]` entries defining tiles (id, name, scene path, min/max grid spans).
+- Each plugin folder contains a `plugin.cfg` INI file with `[plugin]` metadata, `[tile_N]` entries defining tiles, and optional `[settings]` section.
 - Tile IDs are scoped as `{plugin_id}/{tile_id}` to guarantee global uniqueness.
-- `PluginManager.instantiate_tile(tile_id)` loads the tile scene, instantiates it, and tags the root node with `tile_id` and `tile_config` metadata.
+- `PluginManager.instantiate_tile(tile_id)` loads the tile scene, instantiates it, and tags the root node with `tile_id` and `tile_config` metadata. Returns null if source plugin is inactive.
+- `PluginManager.get_plugin_settings(pid)` — returns setting definitions from manifest.
+- `PluginManager.get_plugin_setting(pid, key, default)` — reads persisted value, falls back to manifest default.
+- `PluginManager.set_plugin_setting(pid, key, value)` — persists to `config/plugin_settings.cfg`, emits `plugin_setting_changed` signal.
+- `plugin_active_changed` signal — emitted when plugin activation state changes via `set_plugin_active(pid, active)`.
 - `scripts/plugin_tile.gd` — class_name `PluginTile`, extends `ModuleBase`. Plugin tiles extend this instead of ModuleBase directly. Stores `tile_id` and `tile_config` properties, also written to node metadata for grid/layout access.
 
+### Plugin Settings
+- Storage: `config/plugin_settings.cfg` using ConfigFile directly (not ConfigManager) to avoid key-flattening conflicts with plugin IDs containing underscores.
+- Manifest `[settings]` section: `count=N`, followed by `[setting_N]` entries with `key`, `label`, `type` (int/float/bool/string), optional `default`, `min`, `max`, `step`.
+- ConfigFile.get_value treats `null` as "no default" — use `has_section_key()` before reading optional keys that may not exist in the manifest.
+- Settings auto-save on every change (no Apply/Cancel pattern).
+
 ### Layout System
 - `autoload/layout_manager.gd` — autoload singleton for saving/restoring tile grid positions.
-- Layout files stored as INI in `res://config/layouts/{name}.cfg`. Each entry maps a `tile_id` to `{col, row, w, h}`.
+- Layout files stored as INI in `res://config/layouts/{name}.cfg`. Each entry maps a `tile_id` to `{col, row, w, h}`. `[layout]` section has `grid_columns`/`grid_rows`.
 - `save_layout()` writes the current in-memory layout to disk. `load_layout(name)` reads it back.
 - `switch_layout(name)` saves current layout, loads the named one, emits signals.
 - Current layout name persisted in `ConfigManager` as `layout_current`.
 - Layout auto-saves on every `module_placed` and `module_resized` signal from `DashboardGrid`.
 
 ### Config System
+- `autoload/config_manager.gd` — autoload singleton, wraps ConfigFile for app-wide config.
+- `config/default.cfg` — shipped defaults. `config/config.cfg` — user overrides (gitignored).
+- `ConfigFile` reserved words (`default`, case-insensitive) cannot be used as any value.
 
 ### Splash Screen
 - `scenes/splash.tscn` + `scenes/splash.gd` — entry point (set in `project.godot` as `main_scene`), handles fullscreen, font-size zoom animation, crossfade to dashboard.
@@ -84,6 +99,19 @@ V Panel is a Godot Engine project that builds a fancy real-time status monitor.
 - Flow: Black overlay reveal (0.4s) → font-size animation with TRANS_BACK overshoot (2s) + parallel fade-in (1.8s) → hold (1s) → splash text fades out (1s, EASE_IN) → dashboard instantiated and fades in (1s, EASE_OUT) → reparent to root, queue_free splash.
 - Dashboard background (`PanelContainer`) and splash background (`ColorRect`) both read from `ConfigManager.get_color("background_color")` for a seamless crossfade — no fade-to-black transition.
 
+### Settings Menu
+- `scenes/settings_menu.tscn` + `scenes/settings_menu.gd` — `PopupPanel` with `TabContainer` (General, Plugins, About tabs).
+- Opens as exclusive modal via the ⚙ cog in the tile action menu.
+- Plugins tab: dynamic list showing plugin name, version, Active checkbox, and ⚙ settings cog (only shown if plugin has setting definitions).
+- About tab: project name, version `0.1.0-alpha`, contact, description.
+- `scenes/plugin_settings_popup.tscn` + `.gd` — per-plugin settings popup, opened via cog in Plugins tab. Builds UI dynamically from setting definitions (SpinBox for int/float, CheckBox for bool, LineEdit for string). Settings auto-save on every change.
+
+### Per-Tile Refresh
+- `scenes/dashboard.gd` — per-tile refresh tracking. Base timer ticks at 100ms. Each tile has `update_interval_ms` cached as metadata via `_cache_tile_interval()`.
+- `_tick_refresh()` checks `now - last_refresh >= interval` per tile. Interval defaults to 1000ms, configurable via plugin settings.
+- `_on_plugin_setting_changed()` re-caches intervals on live setting changes.
+- Tween durations in tiles are dynamic: `minf(hardcoded_duration, update_interval_ms / divisor)` — CPU/Memory use divisor 2000, Testing uses 1500.
+
 ### Project Structure
 ```
 res://
@@ -94,24 +122,30 @@ res://
 │   └── textures/    # noise_100.png (tileable Perlin noise for shader distortion)
 ├── autoload/        # Singleton/autoload scripts
 │   ├── config_manager.gd   # INI config via ConfigFile
-│   ├── plugin_manager.gd   # Plugin scanning, tile instantiation
+│   ├── plugin_manager.gd   # Plugin scanning, tile instantiation, settings CRUD
 │   └── layout_manager.gd   # Layout save/load/switch
 ├── config/          # Configuration files (INI format)
 │   ├── default.cfg  # Shipped defaults, tracked in git
 │   ├── config.cfg   # User overrides, gitignored (auto-generated)
+│   ├── plugin_settings.cfg  # Plugin settings storage (auto-created)
 │   └── layouts/     # Saved layout files (*.cfg)
 ├── plugins/         # Plugin folders
-│   └── system_monitor/  # Built-in system monitoring plugin
+│   ├── local_system_monitor/  # CPU + Memory tiles
+│   │   ├── plugin.cfg
+│   │   └── tiles/
+│   │       ├── cpu/
+│   │       └── memory/
+│   └── test/        # Testing tile
 │       ├── plugin.cfg
 │       └── tiles/
-│           ├── cpu/
-│           ├── memory/
 │           └── testing/
 ├── scenes/          # Root scenes
 │   ├── splash.tscn  # Animated splash → dashboard transition
-│   └── dashboard.tscn  # Main dashboard (PanelContainer root)
+│   ├── dashboard.tscn  # Main dashboard (PanelContainer root)
+│   ├── settings_menu.tscn  # Settings popup
+│   └── plugin_settings_popup.tscn  # Per-plugin settings popup
 ├── scripts/         # Shared utility scripts
-│   ├── dashboard_grid.gd   # Responsive grid with drag, resize, preset popup
+│   ├── dashboard_grid.gd   # Responsive grid with drag, resize, long-press, action menu
 │   ├── module_base.gd      # Base class for all modules (mouse_filter IGNORE)
 │   ├── panel_base.gd       # Base class for panels
 │   ├── plugin_tile.gd      # Base class for plugin tiles (extends ModuleBase)
@@ -129,6 +163,9 @@ res://
 - `mouse_exited` signal connected on the grid — aborts drag/resize if the mouse leaves the grid area.
 - `_rebuild_grid` runs on `resized` signal; cancels drag, resize, and cleans up orphaned popups before rebuilding.
 - Shader `corner_radius` is in UV space (0–0.5) where 0.05 ≈ 12px on a 240px‑tall cell.
+- ConfigFile `get_value(section, key, null)` treats `null` as "no default" — use `has_section_key()` for optional fields.
+- `Button.custom_minimum_size` is the writable property (not `minimum_size` or `custom_min_size`).
+- `default` is a reserved ConfigFile keyword case-insensitively — cannot be used as any value.
 
 ### Git Workflow
 - Main branch: `main`