feat: Implement facing profiles and bend direction toggles in test harness

- Added functionality for skeleton IK bone switches, allowing users to dynamically change the bend direction of joints via a context menu.
- Introduced facing profiles (LEFT, RIGHT, FORWARD) that modify the bend direction of limbs based on the selected profile.
- Implemented body part z-ordering based on the facing profile, ensuring correct rendering order of limbs relative to the torso.
- Added a coordinates display panel that shows the position and rotation of the Skeleton2D and its bones, as well as IK target positions.
- Created a new script to generate a walk animation for the stickman rig, including keyframe tracks for various IK targets.
- Updated documentation to reflect the new features and their specifications.

AGENTS.md

@@ -256,6 +256,78 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
     overlay also draws a **null-guarded semi-transparent yellow aim line** from the Head bone
     origin to the head marker (`_draw_ik_handles`, width `1.5/zoom`, alpha `0.5`) — a visual aid
     for the LookAt test.
+  - **Phase 9 Task 1 skeleton IK bone switches:** adds a "Facing" `MenuButton` (leftmost control
+    in the top-bar `HBox`) and per-joint bend-direction toggles for the rig's TwoBoneIK "Flip
+    Bend Direction" flags. `enum FacingProfile { LEFT, RIGHT, FORWARD }` (values used directly as
+    menu item ids); `BEND_JOINTS: Array[String] = ["LeftArm","RightArm","LeftLeg","RightLeg"]`
+    with `BEND_JOINT_BONE_PATHS` (each joint → its lower `Bone2D` NodePath relative to
+    `Skeleton2D`, e.g. `Torso/LeftUpperArm/LeftLowerArm`); `PROFILE_FLAGS` maps each profile to a
+    per-joint `flip_bend_direction` set (LEFT: arms off / legs on; RIGHT: arms on / legs off;
+    FORWARD: LeftArm off, RightArm on, LeftLeg on, RightLeg off — matching `master_rig.tscn`'s
+    authored defaults). State `_facing_profile` (default `FORWARD`, harness-level, persists across
+    spawns), `_context_joint`, `_bend_joint_bones`, `_bend_modifications`, `_facing_button`/
+    `_facing_menu`, `_context_menu`. The Facing popup (Left/Right/Forward) uses dynamic text-only
+    labels with the current profile prefixed `[√] `, refreshed on `about_to_popup` and after
+    selection (mirroring the editor's snap-menu pattern). Runtime resolution:
+    `_resolve_bend_joints()` (called from `_resolve_rig_nodes()`) resolves the 4 lower-limb
+    `Bone2D`s via `get_node_or_null` and matches each `SkeletonModification2DTwoBoneIK` in the
+    modification stack by its `joint_two_bone2d_node` NodePath (no hardcoded stack index);
+    `push_warning` on missing nodes/mods. Per-joint toggle: right-click inside the viewport on an
+    elbow/knee (the upper↔lower limb connector, within `JOINT_HIT_RADIUS_PX := 14.0` screen px
+    converted to world by `_camera.zoom.x`, nearest joint wins) pops a one-item context menu
+    labeled **"Normal Bend"** (when `flip_bend_direction` is currently true) or **"Invert Bend"**
+    (when false); selecting toggles that joint's `flip_bend_direction` on the live TwoBoneIK
+    modification. Only the 4 elbows/knees are right-click targets — shoulders/hips/wrists/ankles/
+    head/torso are not. Lifecycle: `_free_current_rig()` clears `_bend_joint_bones`/
+    `_bend_modifications`/`_context_joint`; `_load_and_spawn()` re-applies
+    `_apply_facing_profile(_facing_profile)` right after `_ensure_modification_stack_enabled()` so
+    every fresh spawn matches the current profile. No persistence to disk.
+  - **Phase 9 Task 2 body-part z-order:** `_apply_facing_profile()` now also sets the
+    `_facing_profile` state itself (previously only the menu handler did) and calls
+    `_apply_body_z_order()`, so bend flags + draw order stay in sync from one entry point.
+    `const BODY_CONTAINER_PATH := "Body"` and `const Z_ORDER_BY_PROFILE: Dictionary` map each
+    `FacingProfile` to the rig `Body/*` visual part node names in **back-to-front draw order**
+    (Godot 4 `Node2D` draws siblings in tree order; all parts keep `z_index = 0`). FORWARD:
+    torso → left/right upper legs → left/right lower legs → left/right upper arms → left/right
+    lower arms → head (all limbs in front of the torso); LEFT: left arm pair then left leg
+    pair **behind** the torso, right leg pair then right arm pair in front; RIGHT: mirrored.
+    In every profile upper limbs stay behind lower limbs; far-side (behind-torso) arms draw
+    behind the legs while near-side arms draw in front of the legs; the **head is always
+    frontmost**. State `_body_container: Node2D` (resolved in
+    `_resolve_rig_nodes()` via `get_node_or_null`, null-guarded with `push_warning`, cleared
+    in `_free_current_rig()`). `_apply_body_z_order()` walks the profile array back-to-front
+    and `move_child(part, count - 1)`s each existing child (missing parts skipped), which
+    yields the profile order; unknown extra children stay at the back. Safe with the adapter:
+    shapes are children of the part nodes, so moving a part moves its whole shape group. No
+    persistence to disk.
+  - **Phase 9 Task 3 coordinates display:** adds a "Show Coords" `CheckBox` in the top-bar
+    `HBox` (after "Show IK Handles", before the status label), default ON, toggled via
+    `_on_show_coords_toggled(pressed)` (sets `_show_coords: bool = true`, flips
+    `_coords_panel.visible`). A code-built right-side readout (`_build_coords_panel()`, called
+    from `_build_ui()` after the viewport container so it renders in front): `_coords_panel`
+    (`PanelContainer`) + monospace selectable `_coords_label` (`RichTextLabel`,
+    `selection_enabled` + `context_menu_enabled` + `fit_content`, autowrap off, scroll off,
+    `FOCUS_CLICK`; `SystemFont`: Consolas/Menlo/DejaVu Sans Mono/Courier New via the
+    `normal_font`/`normal_font_size` (18) theme overrides), anchored `PRESET_TOP_RIGHT`,
+    `offset_top = 40.0`, `offset_right = -8.0`, `offset_left = -COORDS_PANEL_WIDTH` (320.0),
+    `grow_vertical = GROW_DIRECTION_END` + `grow_horizontal = GROW_DIRECTION_BEGIN`
+    (auto-height/width, grows left so text never runs off-screen), `mouse_filter =
+    MOUSE_FILTER_IGNORE` on the panel (the label itself stays interactive for selection);
+    StyleBoxFlat
+    bg `Color(0,0,0,0.55)`, border `Color(1,1,1,0.12)` w1, corner radius 4, content margin 8.
+    Consts `COORDS_PANEL_WIDTH := 320.0` and `COORD_BONE_PATHS` (10 Skeleton2D-relative bone
+    paths: Torso, Torso/Head, both upper/lower arms, both upper/lower legs). State
+    `_coord_bones: Dictionary` (bone display name → `Bone2D`, keyed by `path.get_file()`),
+    `_show_coords`. `_resolve_rig_nodes()` calls `_resolve_coord_bones()` (via
+    `_skeleton.get_node_or_null`, `push_warning` on missing); `_free_current_rig()` clears
+    `_coord_bones` (toggle persists across respawns). `_process(delta)` early-outs when hidden
+    or label null, else `_update_coords_display()` — sections "Skeleton2D" pos + rot deg,
+    "Bones" pos + rot deg, "IK Targets" pos only (reusing `IK_HANDLE_PATHS`/`_ik_handles`);
+    "No rig loaded" fallback; every read guarded with `is_instance_valid`; the label text is
+    only reassigned when the built string changes, so an active text selection survives idle
+    frames. Values are
+    world-space (`global_position`/`global_rotation`), rotation in degrees via
+    `_fmt_deg(rad)` (1 decimal, `°`), `_fmt_vec2(v)` for positions. No persistence to disk.
 - Scenes:
   - `scenes/stickman_editor.tscn` — main editor layout; unique-name nodes (`%Prefix`) used
     for typed `@onready` access: `%MenuBar`, `%StickmanNameEdit`, `%LeftColumn`,
@@ -269,7 +341,8 @@ assembled in a "Whole Stickman" preview that supports translation, rotation, and
     height in their parent VBoxContainer.
   - `scenes/test_harness.tscn` — **standalone staging scene** (Phase 9, not wired into the
     editor; run via **F6**). Backed by `scripts/test_harness.gd`. Top UI bar with file open /
-    quick-select, "Show Bones" / "Show IK Handles" toggles, and a loaded-filename status label;
+    quick-select, "Show Bones" / "Show IK Handles" / "Show Coords" toggles, and a
+    loaded-filename status label;
     `SubViewport` world with an enabled `Camera2D` (middle-mouse pan, wheel zoom, recenter on
     spawn); interactive limb IK via `SkeletonModificationStack2D` TwoBoneIK.