feat: complete Dirigent rename + all TASKLIST items

- Task 1: Identity prompt now includes Discord userId
- Task 2: Added configurable schedulingIdentifier (default: ➡️)
- Task 3: Moderator handoff uses <@userId>+identifier instead of semantic messages
- Task 4: All prompts/comments/help text converted to English
- Task 5: Full project rename WhisperGate → Dirigent across all files

Breaking: config key changed from plugins.entries.whispergate to plugins.entries.dirigent
Breaking: channel policies file renamed to dirigent-channel-policies.json
Breaking: tool name changed from whispergate_tools to dirigent_tools

docs/PR_SUMMARY.md

@@ -1,15 +1,15 @@
-# PR Summary (WhisperGate + Discord Control)
+# PR Summary (Dirigent + Discord Control)
 
 ## Scope
 
 This PR delivers two tracks:
 
-1. WhisperGate deterministic no-reply gate for Discord sessions
+1. Dirigent deterministic no-reply gate for Discord sessions
 2. Discord control extension API for private-channel/member-list gaps
 
 ## Delivered Features
 
-### WhisperGate
+### Dirigent
 
 - Deterministic rule chain:
   1) non-discord => skip