restructure handbook to flat-page spec

Replace the four-section dir layout with the revised flat-page spec:
- Three-page nav: Libraries, Standards, Deploy.
- libraries.md: live client-side fetch of the rethink-public org from the
  Gitea API, denylist-filtered, sorted table linking each repo, no version
  pins, graceful fallback on fetch/CORS failure.
- standards.md: house coding standards.
- deploy.md: deploy guide for rethink-net (services uid 1337, uid-agnostic
  Docker, paths/mounts, bind-mount permissions, read-only secrets).
- index.md landing card grid updated for the three sections.
- gitignore Playwright MCP artifacts.

Verified: mkdocs build --strict clean; libraries fallback renders live.
Signed-off-by: disqualifier <dev@disqualifier.me>

docs/deploy/index.md

@@ -1,22 +0,0 @@
-# Deploy
-
-Guides for getting a service from a repo to running behind the reverse proxy.
-
-!!! note "Work in progress"
-    The services-container deploy guide will live here. Until it's added, this
-    page is a placeholder.
-
-## Planned guides
-
-- **Services container standard** — the baseline image, `uid 1337`, volume and
-  log layout, healthchecks.
-- **Compose pattern** — how a service's `compose.yaml` wires into the shared
-  proxy network.
-- **Reverse proxy** — exposing a service at a subdomain (sanitized).
-
-## Conventions
-
-- Containers run as the services uid (`1337`) per our container standard.
-- Logs land under `/srv/logs/...` mirroring the app's deploy path.
-- No real hostnames, internal IPs, or exact topology in these public pages —
-  use placeholders and describe the pattern.