fix: address shape mounting issues in StkRigAdapter

- Implement anisotropic scaling for shape mounting to prevent distortion.
- Replace bounding-box midpoint anchors with joint-based anchors for correct rotation.
- Reset node transforms to ensure clean scaling and rotation before mounting shapes.
- Introduce new helper functions for computing bounding boxes, anchors, part lengths, and scales.
- Neutralize driver rotations to maintain a consistent frame of reference during shape mounting.
- Update documentation to reflect changes and provide detailed bugfix specifications.

README.md

@@ -397,7 +397,7 @@ Behavior:
 | `res://scenes/stickman_editor.tscn` | **Main scene** — editor layout, File/Edit/View menu bar, dialogs (`GridConfigDialog` + SpinBox), column containers (unique-name nodes). |
 | `res://scenes/body_part_panel.tscn` | Reusable single body-part editor panel (title, drawing area, context menu, `ColorPickerPopup`); expands vertically in its column. |
 | `res://scripts/stickman_editor.gd` | Editor controller — File/Edit/View menu actions, save/load/clear, JSON v1.4 serialization with multi-shape/rotation/scale, `part_order`, and Phase 8 `proportions`/`pivot`/`length`, `settings.json` load/save, editor-wide shape clipboard (Copy/Paste across panels), broadcast of grid/snap settings to panels, Reset Views, populates panels, coordinates selection across panels. |
-| `res://scripts/stk_rig_adapter.gd` | **Phase 8, extended by Phase 9.** Standalone runtime adapter (`class_name StkRigAdapter`, `static func apply(stk_data, rig)`): fits an instantiated `master_rig.tscn` to a loaded `.stk` by re-fitting the 8 limb bones (`Skeleton2D/Torso/...` `Bone2D` lengths + lower-bone origins), recalibrating the IK targets (`IK_Targets/Left|Right_Hand`, `Left|Right_Leg`), mounting the `.stk` shapes onto the `Body/*` visual nodes (open shapes → `Line2D`, closed → `Polygon2D` fill + `Line2D` outline, width 16), and (Phase 9) fitting the head bone (`Head.position.y = -proportions.torso_length`) while mounting the head as **full geometry** — it clears the head's inline `@tool` circle script and mounts `.stk` head shapes as `Line2D`/`Polygon2D`. **Not used by the editor** — consumed by the runtime pipeline. |
+| `res://scripts/stk_rig_adapter.gd` | **Phase 8, extended by Phase 9 (Round 1 bugfix).** Standalone runtime adapter (`class_name StkRigAdapter`, `static func apply(stk_data, rig)`): fits an instantiated `master_rig.tscn` to a loaded `.stk` by re-fitting the 8 limb bones (`Skeleton2D/Torso/...` `Bone2D` lengths + lower-bone origins), recalibrating the IK targets (`IK_Targets/Left|Right_Hand`, `Left|Right_Leg`), neutralizing the `RemoteTransform2D` driver rotations (`update_rotation = false` on the 10 `Body/*` drivers), and mounting the `.stk` shapes onto the `Body/*` visual nodes (open shapes → `Line2D`, closed → `Polygon2D` fill + `Line2D` outline, width 16). Shape mounting recomputes each part's bounding box at mount time (file `pivot`/`length` are no longer trusted), derives **joint-based anchors** per part family (head bottom-center, torso/legs top-center, arms shoulder-end), applies **anisotropic scaling** along the bone's primary axis only (arms X, legs/torso Y; head unscaled; divide-by-zero guard → `1.0`), and resets each `Body/*` container's scale to `(1,1)` / rotation `0` (position untouched). (Phase 9) also fits the head bone (`Head.position.y = -proportions.torso_length`) while mounting the head as **full geometry** — it clears the head's inline `@tool` circle script and mounts `.stk` head shapes as `Line2D`/`Polygon2D`. **Not used by the editor** — consumed by the runtime pipeline. |
 | `res://scripts/stickman_factory.gd` | **Phase 9.** Runtime entry point (`class_name StickmanFactory`, `extends RefCounted`); a static factory that turns a `.stk` file into a live, rigged `master_rig.tscn` instance. `load_stk(path)` reads + parses the file (`{}` + `push_warning` on failure); `spawn_from_data(stk_data)` instantiates `res://master_rig.tscn` and calls `StkRigAdapter.apply(stk_data, rig)`; `spawn(path)` chains them (`null` on empty data). **Not used by the editor.** |
 | `res://scripts/test_harness.gd` | **Phase 9.** Standalone staging scene (run via **F6** on `res://scenes/test_harness.tscn`, not wired into the editor) for debugging bone scales, vector-drawing offsets, and IK limits in isolation. Top UI bar: "Open .stk…" / quick-select buttons (`stickmen/break.stk`, `stickmen/basic.stk`, `stickmen/test.stk`), "Show Bones" / "Show IK Handles" toggles, loaded-filename label. `SubViewport` world + enabled `Camera2D` (middle-mouse pan, wheel zoom, recenter on spawn); each load frees the previous rig and spawns a fresh one via `StickmanFactory.spawn()`. A world-space debug overlay draws bone lines and IK-target markers; the 4 limb `Marker2D` IK targets are click-draggable, flexing limbs live via `SkeletonModificationStack2D` TwoBoneIK (enabled after each spawn). |
 | `res://scenes/test_harness.tscn` | **Phase 9.** Standalone staging scene backing `scripts/test_harness.gd` (run via **F6**; not wired into the editor). |
@@ -485,3 +485,5 @@ BodyPartPanel.shape_selected() ---(bound to part_name)---> stickman_editor
 > **Phase 8:** The `.stk` export evolved to **v1.4** with write-only metadata the editor never reads back. A top-level `proportions` object stores the 5 master-rig rest-pose bone lengths (`upper_arm_length` 168.0, `lower_arm_length` 200.0, `upper_leg_length` 200.0, `lower_leg_length` 200.0, `torso_length` 391.5) — hardcoded constants from `master_rig.tscn`, not measured from the user's shapes. Each `body_parts` entry gains `pivot` (local bounding-box center = rotation origin) and `length` (bbox extent along the segment axis: width for arms, height for torso/legs/head). v1.0–v1.3 files load unchanged and gain these keys on their next save. A new standalone `res://scripts/stk_rig_adapter.gd` (`class_name StkRigAdapter`) fits an instantiated `master_rig.tscn` to a loaded `.stk` (bone fitting + IK recalibration + visual shape mount); it is **not** used by the editor and is reserved for a future runtime pipeline.
 
 > **Phase 9:** Adds the **runtime pipeline** for turning a `.stk` file into a live, rigged `master_rig.tscn` instance, plus a standalone staging scene to debug it. A new `res://scripts/stickman_factory.gd` (`class_name StickmanFactory`) provides the runtime entry point: `load_stk(path)` reads/parses a `.stk` (`FileAccess` + `JSON.parse_string`, `{}` + `push_warning` on failure), `spawn_from_data(stk_data)` instantiates `master_rig.tscn` and applies `StkRigAdapter.apply(stk_data, rig)`, and `spawn(path)` chains them (`null` on empty data). `StkRigAdapter` is extended to also fit the head bone (`Head.position.y = -proportions.torso_length`) and to mount the head as **full geometry** like every other part — clearing its inline `@tool` circle script and mounting `.stk` head shapes as `Line2D`/`Polygon2D` (removed the dead `_mount_head_circle`, `_compute_shapes_bbox`, and `_first_shape_color` helpers). A new standalone scene/resource pair, `res://scenes/test_harness.tscn` + `res://scripts/test_harness.gd` (run via **F6**), loads `.stk` files (open dialog + quick-select for `stickmen/break.stk`, `stickmen/basic.stk`, `stickmen/test.stk`), toggles a world-space debug overlay (bone lines + IK-target markers), pans/zooms a `Camera2D`, and lets you click-drag the 4 limb IK targets with live TwoBoneIK flexing (`SkeletonModificationStack2D` enabled on spawn). Neither the factory nor the harness is wired into the editor. **No `.stk` format change** — `FILE_VERSION` stays `"1.4"`.
+
+> **Phase 9 Round 1 bugfix:** `StkRigAdapter._mount_shapes()` no longer trusts the file's `pivot`/`length`; it recomputes each part's bounding box at mount time and applies **joint-based anchors** (head bottom-center, torso/legs top-center, arms shoulder-end) with **anisotropic scaling** along the bone's primary axis only (arms X, legs/torso Y, head unscaled, divide-by-zero guard → `1.0`). `Body/*` container transforms are reset (scale `(1,1)`, rotation `0`, position untouched) and `_neutralize_driver_rotations()` sets `update_rotation = false` on the 10 `RemoteTransform2D` drivers before mounting. Per docs/phase9_round1_bugfix_spec.md; verified with a 37-assertion headless smoke test.