fix(client): address PR #38 review — 6 warnings + 4 suggestions

Hoshe:
- COLOR_FADE_DURATION 0.7 → 0.5 to match D-033 spec ("0.5s fade")
- Gauntlet guard tests now exercise InputMapper._unhandled_input()
  with synthesized InputEventKey instead of asserting a bool
- Buffer clearing tests use SimBridge pipeline instead of manual nulls
- Add mid-transition re-trigger test (rapid relationship changes)
- Add relationship field to test snapshot NPC

Tyre:
- Add _teleport_in_progress flag to defer smoothing re-enable by one
  frame after teleport (prevents same-_process() re-enable race)
- Add _test_gauntlet_mode to SimBridge test snapshot
- Extract TELEPORT_DISTANCE_THRESHOLD constant, mirror in tests
- Add comments: flash preemption, modulate/color independence
- Rename "hub teleport" → "Gauntlet dev teleport" in code comments
  to clarify this is not production fast-travel

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

client/scripts/autoloads/input_mapper.gd

@@ -20,7 +20,7 @@ enum Action {
 	TOGGLE_STANCE_UP, TOGGLE_STANCE_DOWN,
 	BUG_REPORT,  # #495: F12 WRONG button — client-only, not sent to server
 	SET_FACING,  # D-054: facing octant update (no movement)
-	TELEPORT_HUB,  # #501: Home key — teleport to hub (Gauntlet-only)
+	TELEPORT_HUB,  # #501: Home key — Gauntlet dev teleport (not production fast-travel)
 }
 
 var input_queue: Array[Dictionary] = []