docs(outline): add AI agent context set (Outline layer)

Add docs/outline/00-index.md plus system overview, config/env, code map,
and agent runbook in Simplified Technical English. Link the set from the
README. Completes the project-docs Outline layer.

docs/outline/00-index.md

@@ -0,0 +1,39 @@
+# obsidian-sorter — AI Document Index & Context
+
+> **Target**: AI Agents
+> **Writing Style**: ASD-STE100 Simplified Technical English (`ste-writing`). Brief, terse, active voice.
+
+## 📚 Document Catalog (Inject Specific Document)
+
+Read this index to inject the exact file you need. Do not search all files.
+
+| Document Title | Path | Scope / Description |
+| :--- | :--- | :--- |
+| **System Overview** | `docs/outline/01-system-overview.md` | Explains project purpose, main architecture, and active services. |
+| **Configuration & Env** | `docs/outline/02-config-and-env.md` | Lists environment variables, config paths, log paths, and secrets. |
+| **Code Structure Map** | `docs/outline/03-code-map.md` | Shows folder structure, core entry points, and primary dependencies. |
+| **AI Agent Runbook** | `docs/outline/04-agent-runbook.md` | Gives step-by-step commands to build, test, and restart agent work. |
+
+---
+
+## 🎯 System Summary
+
+`obsidian-sorter` files notes into an Obsidian vault. A note enters `010 inbox/`.
+A watcher proposes a destination. The owner approves the proposal. The writer
+moves the note and updates the Table of Contents. Nothing moves without approval.
+
+The code uses the Python standard library only. Hosts need no pip.
+
+## ⚙️ Core Configuration
+
+- **Env File**: `~/.config/environment.d/*.conf`, or `~/.config/obsidian-sorter/secrets.conf`
+- **Config Directory**: `~/obsidian-sorter/` (deployed code)
+- **Active Ports**: None. The sorter opens no listening port. It calls `api.typesafe.ai` over outbound HTTPS.
+
+## 🔄 Agent Restart Steps
+
+1. Read the Document Catalog above. Inject only required files.
+2. Check git status: `git status`.
+3. Check recent commits: `git log -n 5 --oneline`.
+4. Run validation test: `python3 tests/run_tests.py --no-jev`.
+5. Restart the watcher: `systemctl --user restart obsidian-sorter`.