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/TASKS.json

@@ -0,0 +1,29 @@
+[
+  {
+    "id": "t_jwsoMn5b",
+    "title": "Test Item 1",
+    "description": null,
+    "status": "todo",
+    "priority": "normal",
+    "created_at": "2026-03-19T03:19:37.106698+00:00",
+    "updated_at": "2026-03-19T03:19:37.106708+00:00"
+  },
+  {
+    "id": "t_ptw8nDec",
+    "title": "Test Item 2",
+    "description": null,
+    "status": "todo",
+    "priority": "normal",
+    "created_at": "2026-03-19T03:19:37.753740+00:00",
+    "updated_at": "2026-03-19T03:19:37.753750+00:00"
+  },
+  {
+    "id": "t_1ZToczGC",
+    "title": "Create scratch pad toolset idea",
+    "description": null,
+    "status": "todo",
+    "priority": "normal",
+    "created_at": "2026-03-20T05:14:37.344354+00:00",
+    "updated_at": "2026-03-20T05:14:37.344368+00:00"
+  }
+]