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/context_loader.py

@@ -1,5 +1,4 @@
-from pathlib import Path
-from config import settings
+from persona import persona_path
 
 
 # Core identity files — always loaded regardless of tier
@@ -26,7 +25,7 @@ def load_context(
     Tier 3  — + last 2 raw session logs             (~15,000 tokens)
     Tier 4  — + last 7 raw session logs             (~50,000 tokens)
     """
-    inara_dir = settings.inara_path()
+    inara_dir = persona_path()
     parts = []
 
     # ── 1. Core identity (always) ──────────────────────────────────