feat(ui): knowledge/journal display panel (#264)

Right-side insert panel toggled with J key. Facts grouped by entity
with confidence, source, and state metadata. Contradicted entries
in amber with strikethrough (THE FRIEND arc surface). Stale entries
dimmed. Mutual exclusion with dialogue box. All labels via UIStrings.

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

client/scripts/autoloads/input_mapper.gd

@@ -19,6 +19,7 @@ enum Action {
 	INTERACT, USE_PERCEPTION_MODE, OPEN_MENU, PAUSE, UNPAUSE,
 	TOGGLE_STANCE_UP, TOGGLE_STANCE_DOWN,
 	BUG_REPORT,  # #495: F12 WRONG button — client-only, not sent to server
+	OPEN_JOURNAL,  # #264: J key — toggle knowledge journal panel, client-only
 	SET_FACING,  # D-054: facing octant update (no movement)
 	TELEPORT_HUB,  # #501: Home key — Gauntlet dev teleport (not production fast-travel)
 }
@@ -106,6 +107,8 @@ func _unhandled_input(event: InputEvent) -> void:
 		action = Action.TOGGLE_STANCE_DOWN
 	elif event.is_action_pressed("bug_report"):
 		action = Action.BUG_REPORT
+	elif event.is_action_pressed("open_journal"):
+		action = Action.OPEN_JOURNAL
 	elif event.is_action_pressed("teleport_hub"):
 		if GameState.gauntlet_mode:
 			action = Action.TELEPORT_HUB