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>

personas/inara/sessions/2026-03-06.md

@@ -0,0 +1,10 @@
+# Session Log — 2026-03-06
+
+### [03:21] `6974b48d`
+**Scott:** This is a test note
+
+**Inara:** Noted. ✨
+
+Markdown rendered cleanly on my end — tables, code blocks, blockquotes, the works. If you're testing the UI or a new client surface, looks like we're green across the board.
+
+Anything you actually need, or just shaking the tires?