feat: multi-user/multi-persona support with two-level home directory layout

Restructures persona storage from a flat personas/{name}/ layout to
home/{username}/persona/{name}/, mirroring Linux home directories.

Changes:
- persona.py: two ContextVars (user + persona), Linux-style name validation,
  set_context(), get_user(), get_persona(), validate(), list_users(),
  list_user_personas(); persona_path() takes (username, name)
- config.py: replaces personas_dir with home_dir + home_root()
- git mv personas/inara → home/scott/persona/inara (history preserved)
- home/holly/persona/tina/: Holly's persona stub added
- cron_runner.py: all storage functions take (username, persona) params
- tools/cron.py: stamps user + persona on jobs; APScheduler IDs are
  {user}:{persona}:{job_id} to prevent collisions across users
- memory_distiller.py: distill_short/mid/long take (username, persona);
  added missing Path + settings imports
- scheduler.py: _load_user_crons() iterates home/*/persona/* (two-level)
- routers/chat.py, orchestrator.py: user field added; set_context() called
- tests/conftest.py: home_root fixture with two-level structure;
  patches home_dir instead of personas_dir
- tests/test_persona.py: fully rewritten for two-level API
- tests/test_api_files.py: updated fixture name and path
- .env.default: documents HOME_DIR setting; scrubs stale API key
- CLAUDE.md, README.md: directory maps updated for new layout

All 80 tests pass.

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

home/scott/persona/inara/sessions/2026-03-05.md

@@ -0,0 +1,128 @@
+# Session Log — 2026-03-05
+
+### [23:42] `051d6908`
+**Scott:** Please respond with some Markdown so we can make sure it renders.
+
+**Inara:** # Markdown Rendering Test ✨
+
+Here's a little showcase to confirm everything renders properly.
+
+---
+
+## Text Formatting
+
+This is **bold**, this is *italic*, and this is ~~strikethrough~~. Inline `code` looks like this.
+
+## Lists
+
+**Unordered:**
+- Cortex orchestration layer
+- WireGuard mesh networking
+- Self-hosted everything
+
+**Ordered:**
+1. Request
+2. Acknowledge
+3. Result
+
+## Code Block
+
+```python
+def greet(name: str) -> str:
+    return f"Hello from Inara, {name}."
+
+print(greet("Scott"))
+```
+
+## Table
+
+| Agent ID     | Machine       | Role                  |
+|--------------|---------------|-----------------------|
+| `scott_lpt`  | Main Laptop   | General Manager       |
+| `scott_wks`  | Workstation   | Operations Commander  |
+| `scott_gaming` | Gaming Laptop | Local LLM / Ollama  |
+
+## Blockquote
+
+> *"You can't take the sky from me."*
+
+## Nested List
+
+- Infrastructure
+  - Docker + Compose
+  - Nginx reverse proxy
+  - MariaDB backend
+- Agents
+  - Inara (me)
+  - Fleet nodes via Syncthing
+
+---
+
+Looks good from my end — let me know if anything isn't rendering as expected.
+
+### [23:44] `6974b48d`
+**Scott:** Please respond with some Markdown so we can make sure it renders.
+
+**Inara:** # Hello from Inara ✨
+
+Here's a tour of Markdown rendering:
+
+---
+
+## Text Formatting
+
+This is **bold**, this is *italic*, and this is `inline code`. You can also do ~~strikethrough~~.
+
+---
+
+## Lists
+
+**Unordered:**
+- WireGuard mesh
+- pfSense + VLANs
+- Syncthing sync
+  - Nested item
+  - Another nested item
+
+**Ordered:**
+1. Request
+2. Acknowledge
+3. Result
+
+---
+
+## Code Block
+
+```python
+def greet(name: str) -> str:
+    return f"Hello, {name}. Fancy meeting you here."
+
+print(greet("Scott"))
+```
+
+---
+
+## Table
+
+| Agent | Machine | Role |
+|-------|---------|------|
+| `inara` | TBD | Primary conversational agent |
+| `scott_lpt` | Main Laptop | General Manager |
+| `scott_wks` | Workstation | Operations Commander |
+
+---
+
+## Blockquote
+
+> *"You're welcome on my boat. God ain't."*
+> — Mal Reynolds
+
+---
+
+## Links & Inline Elements
+
+Check the [Firefly wiki](https://firefly.fandom.com) — not that you need it. The ship is called **Serenity**. The signal can't be stopped.
+
+---
+
+Looks like everything's rendering. We're good to go. 🚀