docs: add wiki and refresh flat lib with mcp artifacts

- Add hand-written wiki (index, overview, how-to, extending, dev)
  following the platform anatomy
- Remove stale nested docs/lib/mail_intake and regenerate the flat
  lib reference to match docforge.nav.yml
- Regenerate MCP bundle with standardized docstrings

docs/wiki/04_development.md

@@ -0,0 +1,88 @@
+# 🛠️ Development
+
+Working on `mail-intake` itself.
+
+---
+
+## 📂 Repository layout
+
+| Path | Purpose |
+|---|---|
+| `mail_intake/` | The library package (adapters, auth, credentials, parsers, ingestion, models) |
+| `mail_intake/*.pyi` | Type stubs kept in sync with implementations |
+| `tests/` | Unit and integration tests (mock transports, no live mail) |
+| `docs/lib/` | Generated library reference (docforge, flat layout) |
+| `docs/mcp/` | Machine-readable bundle served by the MCP server |
+| `docs/wiki/` | This hand-written wiki |
+
+---
+
+## 🔧 Setup
+
+```bash
+python -m venv .venv
+.venv/Scripts/pip install -e ".[dev]"
+```
+
+> OAuth credential files (`credentials*.json`, `token.pickle`,
+> `client_secret_*.json`) are gitignored — keep them out of the repository.
+
+---
+
+## 🧪 Tests
+
+Run the suite (no network or live Gmail required):
+
+```bash
+.venv/Scripts/pytest
+```
+
+Coverage spans ingestion flows, credential stores, parsers, and auth against
+mock providers.
+
+---
+
+## ✅ Quality gates
+
+The CI quality gate runs, matching the Drone pipeline:
+
+```bash
+.venv/Scripts/black --check .
+.venv/Scripts/ruff check .
+.venv/Scripts/mypy
+.venv/Scripts/pytest
+```
+
+---
+
+## 📝 Building documentation (docforge)
+
+The site is generated by [`docforge`](https://git.aetoskia.com/aetos/doc-forge)
+and served per kind under `site/{kind}`:
+
+```bash
+doc-forge build \
+  --mkdocs --mcp --wiki \
+  --module-is-source --module mail_intake \
+  --site-name "Mail Intake"
+```
+
+- `--module-is-source` renders the flat `docs/lib/` layout (no nesting under
+  `mail_intake/`), matching `docforge.nav.yml` and `docs/mkdocs.lib.yml`.
+- `--mcp` regenerates the structured bundle in `docs/mcp/`.
+- `--wiki` builds this wiki.
+
+Preview locally:
+
+```bash
+doc-forge serve --lib
+doc-forge serve --wiki
+doc-forge serve --mcp
+```
+
+---
+
+## 📚 Read Next
+
+- [Extending Mail Intake](03_extending.md) — custom adapters and stores.
+- [Overview](01_overview.md) — the core architecture.