feat: multi-persona support (single Cortex, multiple users)

- Add cortex/persona.py: ContextVar-based per-request routing with
  path traversal protection and persona validation
- Migrate inara/ → personas/inara/ (git history preserved via git mv)
- config.py: add personas_root(), inara_path() delegates to personas/inara
- All 14 settings.inara_path() call sites replaced with persona_path()
- ChatRequest + OrchestrateRequest: add persona field (default: "inara")
  with validation at request entry before any processing
- memory_distiller: add optional persona param for future per-persona distill
- cron_runner/tools/cron: stamp persona on jobs, prefix APScheduler IDs
  (persona:job_id) to prevent collisions across personas
- scheduler: _load_user_crons() iterates all personas at startup

Adding a new persona: create personas/<name>/ with IDENTITY.md + SOUL.md.
Auth: handled at nginx level (inject X-Cortex-Persona header per subdomain).
Future: persona maps to Aether account_id_random for full integration.

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

cortex/session_logger.py

@@ -1,11 +1,11 @@
-from pathlib import Path
 from datetime import datetime
 from config import settings
+from persona import persona_path
 
 
 def log_turn(session_id: str, user_msg: str, assistant_msg: str) -> None:
     today = datetime.now().strftime("%Y-%m-%d")
-    sessions_dir = settings.inara_path() / "sessions"
+    sessions_dir = persona_path() / "sessions"
     sessions_dir.mkdir(exist_ok=True)
 
     log_file = sessions_dir / f"{today}.md"