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/main.gd

@@ -20,7 +20,8 @@ var _last_dialogue_npc_id: int = -1  # D-064: NPC entity_id for WalkAway input
 var _camera_anchored: bool = false
 var _last_monologue_tick: int = -1  # Prevent re-consuming monologue when same tick polled twice
 var _last_dialogue_tick: int = -1
-var _flash_rect: ColorRect = null  # #502: ephemeral screen flash overlay
+var _flash_rect: ColorRect = null  # #502/#501: ephemeral screen flash overlay (shared: teleport preempts amber)
+var _teleport_in_progress: bool = false  # #501: defer smoothing re-enable by one frame after teleport
 
 func _ready() -> void:
 	print("The Settled Reach — client initialized")
@@ -123,9 +124,15 @@ func _process(_delta: float) -> void:
 	# rendered used smoothing=OFF (correct viewport from frame one). Now we
 	# turn smoothing back on and sync its internal state so subsequent frames
 	# get smooth camera tracking during gameplay.
+	# #501: Skip re-enable during teleport — _teleport_transition() disables
+	# smoothing for a clean camera snap. Defer by one frame to avoid the
+	# re-enable block in the same _process() call undoing the snap.
 	if _camera_anchored and not camera.position_smoothing_enabled:
-		camera.position_smoothing_enabled = true
-		camera.reset_smoothing()
+		if _teleport_in_progress:
+			_teleport_in_progress = false
+		else:
+			camera.position_smoothing_enabled = true
+			camera.reset_smoothing()
 
 	# Send queued input to simulation
 	var inputs = InputMapper.flush_queue()
@@ -236,17 +243,23 @@ func _on_connection_state_changed(old_state: SimBridge.ConnectionState, new_stat
 
 
 # #501: Detect large position jump indicating a teleport (not normal movement).
+const TELEPORT_DISTANCE_THRESHOLD: float = 5.0
+
 func _detect_teleport(old_pos: Vector2, new_pos: Vector2) -> bool:
-	return old_pos.distance_to(new_pos) > 5.0
+	return old_pos.distance_to(new_pos) > TELEPORT_DISTANCE_THRESHOLD
 
 
-# #501: Hub teleport transition — snap camera + 0.3s fade-from-black.
+# #501: Gauntlet dev teleport transition — snap camera + 0.3s fade-from-black.
 # Clears dialogue/monologue/interaction state (server clears its side too).
+# Scoped to Gauntlet testing only — production fast-travel uses diegetic gates.
 func _teleport_transition() -> void:
-	# Snap camera: disable smoothing, force re-anchor
+	# Snap camera: disable smoothing, force re-anchor.
+	# _teleport_in_progress defers smoothing re-enable by one frame so the
+	# re-enable block at the bottom of _process() doesn't undo the snap.
 	camera.position_smoothing_enabled = false
 	camera.global_position = GameState.player_position * Constants.TILE_SIZE
 	_camera_anchored = true
+	_teleport_in_progress = true
 
 	# Clear client-side buffers
 	GameState.current_monologue = null