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/IMPLEMENTATION.md

@@ -1,8 +1,8 @@
-# WhisperGate Implementation Notes
+# Dirigent Implementation Notes
 
 ## Decision path
 
-WhisperGate evaluates in strict order:
+Dirigent evaluates in strict order:
 
 1. channel check (discord-only)
 2. bypass sender check