fix(client): address PR #25 review — 5 critical bugs, 4 warnings, 3 suggestions

Critical fixes:
- hide_dialogue() sent PAUSE instead of UNPAUSE, permanently freezing
  simulation after every dialogue (both reviewers)
- Confrontation monologue hardcoded in GDScript constant, violating
  D-042/D-020 — moved to ui-strings.yaml as dialogue.confrontation_beat
- Walk-away WASD didn't call set_input_as_handled(), letting movement
  event propagate and potentially stepping on the same frame
- is_dialogue_active() returned _is_showing only — interaction list
  could flash during 300ms fade gap. Now includes dialogue_active state
- Removed dead _last_dialogue_id / get_dialogue_id() state (never read)

Warnings addressed:
- Audio registry now scans res://audio/ recursively (subdirs registered)
- add_bus_effect guarded against duplicate calls in tests
- int64 encoder dead code tagged KNOWN-DEFECT, filed as ticket #516
- D-073 zone crossfade stub comment clarifies Sprint 9+ deferral
- listening_focus dip documents caller tick-gate responsibility (D-069/D-071)

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

client/scripts/main.gd

@@ -13,10 +13,6 @@ extends Node2D
 @onready var stance_indicator = $UILayer/StanceIndicator  # D-053: z-layer 7
 @onready var cursor_renderer = $UILayer/CursorRenderer  # D-056: z-layer 7
 
-# Tracks the dialogue_id from dialogue_box to prevent consume-once race during fade-in.
-# If a new snapshot arrives with null dialogue while fade-in is still running,
-# we don't re-trigger show_dialogue because _last_dialogue_id still matches.
-var _last_dialogue_id: int = 0
 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
@@ -169,7 +165,6 @@ func _consume_dialogue() -> void:
 		dlg.get("speech", ""),
 		dlg.get("options", [])
 	)
-	_last_dialogue_id = dialogue_box.get_dialogue_id()
 	GameState.current_dialogue = null