feat(wiki): docs-lookup plugin against Quartz contentIndex

New maubot plugin that points at any Quartz-rendered docs site and
answers chat queries by full-text searching its emitted
/static/contentIndex.json. Default config targets docs.ariege.io
(castle-docs).

Commands:
  !ask <query>            search corpus; top-N hits with snippet + link
  !doc <slug-or-title>    open a specific page (fuzzy title match)
  !wiki / !wiki refresh   status / force re-index

Architecture:
- Periodic fetch (default 10 min) of /static/contentIndex.json
- In-memory inverted-ish scoring: title hit 5pt, content hit 1pt + freq
- No LLM — pure deterministic keyword search; RAG is future Phase 2b
- No DB — index is upstream-derived cache, repopulates on bot restart

Deployment posture: docs.ariege.io is served from cfaun alongside
maubot, so the bot hits it over the host's internal network — works
during WAN outages. base-config.yaml exposes docs_url + index_path
for adopters pointing at their own site.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

wiki/base-config.yaml

@@ -0,0 +1,21 @@
+# Wiki lookup config. Point at any Quartz-emitted site:
+# `docs_url` + `index_path` together resolve to the contentIndex.json
+# the bot uses for search. Page links are constructed from docs_url + slug.
+
+docs_url: https://docs.ariege.io
+index_path: /static/contentIndex.json
+
+# How often to re-fetch the content index, in minutes. Lower = fresher
+# but more network chatter. Site refreshes typically happen on git push,
+# so a few minutes lag is normal.
+refresh_minutes: 10
+
+# Max results returned per `!ask` query.
+max_results: 3
+
+# Snippet window around the first match in `!ask` output, in characters.
+snippet_chars: 160
+
+# Human-readable label for the docs site, used in bot output.
+# E.g. "Castle Docs", "Co-op Wiki", "Operations Manual".
+site_name: Castle Docs