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/01-system-overview.md

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+# obsidian-sorter — System Overview
+
+> **Target**: AI Agents — ASD-STE100 Simplified Technical English.
+
+## Purpose
+
+The sorter files notes into a personal Obsidian vault. The owner drops a note
+into `010 inbox/`. The sorter decides the destination. The owner approves. The
+sorter then moves the note and updates the index. The owner stays in control of
+every move.
+
+## Architecture
+
+The sorter uses two classification tiers. Tier 1 uses deterministic rules. Tier
+2 uses a probabilistic model (TypeSafe JEV). Tier 2 runs only when Tier 1 is
+unsure.
+
+The system has one rule for types: **the type mirrors the folder**. Nothing is
+inferred from content. The destination folder decides the type.
+
+| Folder | Type |
+| :--- | :--- |
+| `200 projects/` | `project` |
+| `300 areas/` | `area` |
+| `400 Personal Family/` | `family` |
+| `100 Table of Contents/` | `index` |
+| `000 daily/` | `daily` |
+| `500 archive/` | `archive` |
+| `Clippings/` | `clipping` |
+| `010 inbox/` | `note` (unsorted placeholder only) |
+
+Retired types (never reintroduce): `subject`, `domain`, `tool`, `service`,
+`container`, `machine`, `storage`, `backup-system`, `network-component`,
+`website`, `person`.
+
+## Flow
+
+1. A note lands in `010 inbox/` with `type: note`.
+2. The watcher polls every 10 seconds. It classifies the note.
+3. The watcher writes the proposal into the note frontmatter.
+4. The owner reviews the note in Obsidian and ticks the `approved` checkbox.
+5. The watcher files the note. It moves the file, strips admin fields, and
+   inserts the Table of Contents entry.
+
+Admin fields written during review: `proposed_folder`, `proposed_toc`,
+`proposed_tags`, `confidence`, `approved`, `proposed_for`. The writer removes
+all admin fields after filing.
+
+## Active Services
+
+| Service | Host | Details |
+| :--- | :--- | :--- |
+| `obsidian-sorter` (systemd user unit) | `.27` | Polls the inbox every 10 seconds. Enabled and lingering. |
+| Command wrapper | `.27` | `~/bin/obsidian-sort` |
+
+The unit runs `~/bin/obsidian-sort watch --interval 10`. It writes to
+`~/.local/state/obsidian-sorter.log`. It restarts on failure after 30 seconds.
+
+## Key Behaviour Rules
+
+- Dry run is the default. The `--apply` flag is required to write anything.
+- Notes named `Untitled*` never move. The plan is blocked.
+- The writer never overwrites an existing destination.
+- The owner's folder choice always wins. The sorter never re-decides a folder
+  that already has a value.
+- The owner's own tags win. A note tagged `project` or `family` stays in that
+  bucket.
+- The writer preserves `tags`, `aliases`, `id`, and `created`.
+- The writer never rewrites the note body.
+- JEV is probabilistic. Folder accuracy is about 74%. Tests assert the bucket
+  strictly. Tests assert the sub-folder only with `--strict-folders`.
+
+## Related Artifacts
+
+- Gitea repository: `https://gitea.lab.audasmedia.com.au/sam/obsidian-sorter`
+- Architecture map: `https://maps.lab.audasmedia.com.au/obsidian-sorter/docs/obsidian-sorter-map.html`
+- Handoff notes: `docs/HANDOFF.md`