Add StkRigAdapter for runtime skeleton fitting and shape mounting

- Implemented StkRigAdapter class to adapt a master rig to a loaded .stk dictionary.
- Added methods for fitting bone lengths, recalibrating IK targets, and mounting vector shapes.
- Defined constants for default proportions and bone paths.
- Included error handling for missing nodes and invalid data structures.

AGENTS.md

@@ -19,9 +19,15 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
 ## Architecture
 - `scripts/stickman_editor.gd` — `extends Control`; the main controller. Owns the menu bar,
   save/load/clear flow, JSON (de)serialization, and populates the 10 body-part panels.
-  Writes `FILE_VERSION "1.2"`; auto-migrates `"1.0"`/`"1.1"` files on load. Coordinates cross-panel
+  Writes `FILE_VERSION "1.4"`; auto-migrates `"1.0"`–`"1.3"` files on load. Coordinates cross-panel
   selection so only one shape is selected at a time (`shape_selected` → deselect others).
-  Collects per-part `{shapes[], position, rotation, scale}` for save/load.
+  Collects per-part `{shapes[], position, rotation, scale, pivot, length}` for save/load.
+  - **Phase 8 save export:** writes top-level `proportions` (hardcoded master-rig rest-pose
+    constants 168/200/200/200/391.5 via the `PROPORTIONS` const) and per-part `pivot`/`length`
+    computed from the panel's local shape bounding box (`_compute_part_pivot_length()`): `pivot` =
+    bbox center, `length` = bbox width for the 4 arm parts (`X_AXIS_PARTS`) and bbox height
+    otherwise. `pivot`/`length`/`proportions` are write-only metadata — never read back on load,
+    recomputed on every save.
   - **Phase 6 recent colors:** stores `_recent_colors: Array[String]` (max 8,
     most-recent-first), loads from `settings.json` (`recent_colors` key) in
     `_load_settings()`, saves on each color selection via `_save_settings()`, and
@@ -37,6 +43,17 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
     `global_to_world(global_pos)`, and writes `"X: ###  Y: ###"` to `_status_cursor_coords`.
   - **Phase 6 snap status:** `_status_snap_status` displays `"SNAP: ON"` / `"SNAP: OFF"`,
     set in `_ready()` and re-synced when snap is toggled (`_on_edit_menu_id_pressed`).
+  - **Phase 7 pose guide toggle:** stores `_show_guide: bool` (default `true`), persisted to
+    `settings.json` under the `show_pose_guide` key (default `true`) via `_load_settings()` /
+    `_save_settings()`. The View menu item (id 1) is a **dynamic, text-only** label (no
+    checkmark): "Hide Pose Guide" while the guide is visible, "Show Pose Guide" while hidden,
+    set via `_guide_menu_label()`. `_update_guide_menu_item()` refreshes only the item text;
+    it is synced on the `about_to_popup` signal (`_on_view_menu_about_to_popup`) and again at
+    the end of `_load_settings()` (so a persisted `show_pose_guide: false` shows "Show Pose
+    Guide" immediately at startup). `_on_view_menu_id_pressed` (id 1) toggles the state, saves,
+    and broadcasts. `_broadcast_settings()` pushes the value to the preview via
+    `WholeStickmanPreview.set_show_guide(_show_guide)` (called in `_ready()` after
+    `_load_settings()`).
 - `scripts/body_part_panel.gd` — `class_name BodyPartPanel`, `extends PanelContainer`.
   Reusable per-part editor. Public API:
   - `set_shape_data(data: Variant)` — import shape data (Array or single Dictionary; used on Load/Clear)
@@ -69,6 +86,36 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
   - **Selection gizmos always on top:** bounding box, rotation circle, and scale
     crosses for the selected part are drawn in a second pass after all parts,
     via `_selected_gizmo_bounds`, so they always render in front.
+- `scripts/whole_stickman_preview.gd` — `class_name WholeStickmanPreview`, `extends Control`;
+  the assembly preview. Owns per-part position/rotation/scale, Z-order (`_part_order`),
+  selection + gizmos, grid drawing, and pan/zoom. Public API includes `set_body_parts()`,
+  `set_show_guide(enabled: bool)`, `reset_view()`, and `is_cursor_over_preview(global_pos)`.
+  - **Phase 7 pose silhouette guide:** `set_show_guide()` stores `_show_guide: bool`
+    (default `true`) and redraws; `_draw_silhouette_guide()` is called in `_on_preview_draw()`
+    after the part loop and before the drag highlight/selection gizmos, so it renders above
+    the grid **and in front of user parts** (ghosting over them), below the selection
+    gizmos and drag highlight. The guide is **centered** at the default view and after
+    `Reset Views`, computed at draw time from the live preview size via
+    `_guide_to_preview()` = `(master_pos - GUIDE_FIGURE_CENTER) * GUIDE_SCALE +
+    preview_area.size * 0.5`, so it also re-centers on window resize; it remains a
+    world-space fixture that moves with pan/zoom. Joint positions are **hardcoded
+    constants** derived from the `master_rig.tscn` rest pose (`GUIDE_JOINTS`: 13 anchors
+    Head/Neck/Shoulders/Elbows/Wrists/Hips/Knees/Ankles;
+    `GUIDE_SCALE = 1.0`, `GUIDE_FIGURE_CENTER = (0, -93.75)`, `GUIDE_HEAD_RADIUS = 100.0`).
+    Color-coded: left limbs cyan-blue `Color(0.35, 0.70, 1.00)`, right limbs orange-red
+    `Color(1.00, 0.50, 0.20)`, central spine/head white, with lines at alpha `0.45` and joint
+    dots at alpha `0.65`. Joint dots use `GUIDE_JOINT_RADIUS / _zoom` (6 px constant screen
+    size). The guide is pure drawing — **no hit-testing** is added, so it never intercepts
+    part dragging/selection.
+- `scripts/stk_rig_adapter.gd` — `class_name StkRigAdapter`, `extends RefCounted`; a **standalone
+  runtime adapter** (Phase 8, **not referenced by the editor**). `static func apply(stk_data, rig)`
+  fits an instantiated `master_rig.tscn` to a loaded `.stk` dictionary, calling three private
+  helpers in order: `_fit_bones` (re-fits the 8 limb `Bone2D` lengths + lower-bone origins),
+  `_recalibrate_ik` (repositions the `IK_Targets/Left|Right_Hand` and `Left|Right_Leg` targets),
+  and `_mount_shapes` (mounts `.stk` shapes onto the `Body/*` visual nodes — open → `Line2D`,
+  closed → `Polygon2D` fill + `Line2D` outline, width 16). Targets `master_rig.tscn` node paths;
+  every node lookup is null-guarded (missing node → `push_warning` + skip, never crash). Consumed
+  by a future runtime pipeline.
 - Scenes:
   - `scenes/stickman_editor.tscn` — main editor layout; unique-name nodes (`%Prefix`) used
     for typed `@onready` access: `%MenuBar`, `%StickmanNameEdit`, `%LeftColumn`,
@@ -95,15 +142,22 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
 - **Phase 4:** A panel stores a `shapes[]` array of shape dictionaries. Z-order = array
   position (first = back, last = front). Per-part data includes `{shapes[], position,
   rotation, scale}`.
-- The JSON `.stk` format is defined in `README.md` (versioned `"1.2"`, extensible;
-  `"1.0"`/`"1.1"` files auto-migrate on load).
+- **Phase 8:** per-part data adds `pivot` `{x, y}` (local bounding-box center = rotation
+  origin) and `length` (float, bbox extent along the segment axis) for format v1.4; the
+  `.stk` root also gains a top-level `proportions` object (5 rig bone lengths). All three
+  are write-only metadata recomputed on every save — never read back on load.
+- The JSON `.stk` format is defined in `README.md` (versioned `"1.4"`, extensible;
+  `"1.0"`–`"1.3"` files auto-migrate on load).
 
 ### settings.json (Phase 6)
 - Persisted editor preferences written to `settings.json` via `_save_settings()` and
   loaded in `_load_settings()`.
-- Keys: `version`, `grid_size`, `snap_to_grid`, `recent_colors`.
+- Keys: `version`, `grid_size`, `snap_to_grid`, `recent_colors`, `show_pose_guide`.
 - `recent_colors: Array[String]` — the last up-to-8 selected hex colors, most-recent-first.
   Populated on load and flushed on every color selection.
+- `show_pose_guide: bool` — whether the pose silhouette guide is visible in the Whole
+  Stickman preview. Default `true`. Loaded in `_load_settings()` and flushed on every toggle
+  via `_broadcast_settings()`.
 
 ### Legacy scene (do not delete)
 - `stick.tscn` — the original rigged/animated figure using `Skeleton2D` + IK targets +