fix(client): address PR #36 review — 10 items from Hoshe + Tyre

Critical:
- deactivate_insert() now called when selecting non-Insert spoke,
  cancelling with no selection, or pressing Escape while insert is
  active. Fixes simulation staying paused permanently after Insert.

Warnings:
- Checklist conditions with empty id excluded from get_results() and
  get_total_count() — prevents impossible-to-complete checklists.
  Warns at load time when empty-id conditions are found.
- _content_base now checks res://content/ first (exported builds),
  falls back to ../content for editor/dev mode.
- 26 new tests for D-054 functions: _angle_to_octant (8 octants),
  _snap_to_octant_dir (9 cases incl. zero/tiny), _wasd_to_world_dir
  (8 facing/movement combos). New test file: test_input_mapper_facing.gd.

Suggestions:
- Cached get_theme_default_font() in checklist overlay _ready().
- Documented InputMapper → GameState coupling as intentional.
- Documented YAML parser # truncation limitation.
- _insert_active reset on Escape dismiss (Tyre #3).
- SimBridge test mode SetFacing reads action_data.facing instead of
  InputMapper global (Tyre #4).
- Removed dead _facing_to_rotation() from entity_renderer.gd (Tyre #5).
- Fixed 2 failing facing indicator tests to use InputMapper.facing_angle
  instead of GameState.player_facing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/scripts/autoloads/input_mapper.gd

@@ -122,6 +122,8 @@ func flush_queue() -> Array[Dictionary]:
 
 # D-054: Compute facing angle from mouse position relative to player screen position.
 # Uses viewport canvas transform to convert world coords to screen coords.
+# Intentional coupling: reads GameState.player_position directly — InputMapper is an
+# autoload that runs before game loop rendering, so position is always current-tick.
 func _update_facing_from_mouse() -> void:
 	var vp := get_viewport()
 	if vp == null: