chore: add project docs, glossary, research and opencode/fastcrw skills

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.claude/skills/fastcrw-search-api/SKILL.md

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+---
+name: fastcrw-search-api
+description: Contract of the fastCRW `POST /v1/search` REST endpoint (auth, request, response shapes, errors, env vars). Use when writing or testing the plugin's search call or its response/error mapping.
+---
+
+# fastCRW `/v1/search`
+
+Researched from docs.fastcrw.com and github.com/us/crw source; not tested against a live instance. Full detail: `docs/research/fastcrw-search-api.md`.
+
+## Call
+
+`POST {baseURL}/v1/search`, `Content-Type: application/json`, body `{ "query": string, "limit": number }`.
+
+- `query` required, max 2000 chars. `limit` default 5, clamped server-side to 1..20.
+- Optional extras worth exposing: `lang`, `tbs` (`qdr:h|d|w|m|y`). Do not send `sources` (switches the response to a grouped shape).
+
+## Auth
+
+`Authorization: Bearer <key>`. Send it only when a key is configured; self-hosted needs none unless the operator set `CRW_AUTH__API_KEYS`. 401 messages: "Missing Authorization header", "Invalid API key".
+
+## Env vars (match upstream names)
+
+`CRW_API_URL` (base URL; hosted default `https://api.fastcrw.com`, self-hosted `http://localhost:3000`), `CRW_API_KEY` (token).
+
+## Response: parse both shapes
+
+```json
+{ "success": true, "data": [ ... ] }
+{ "success": true, "data": { "results": [ ... ] } }
+```
+
+Result: `url`, `title`, `description`, `snippet` (always-populated alias of `description`), `position`, optional `score`, `publishedDate`, `category`. Map to opencode as `{ url, title, content: snippet || description || "", time: {} }`.
+
+## Errors
+
+Body `{ "success": false, "error": string, "error_code": string }`.
+
+| HTTP | error_code |
+|---|---|
+| 400 | `invalid_request` |
+| 401 | auth middleware message |
+| 422 | `target_unreachable` |
+| 429 | `rate_limited` |
+| 500 | `internal_error` |
+| 502 | `http_error` |
+| 503 | `search_disabled` / `search_degraded` |
+| 504 | `timeout` |
+
+Self-hosted search needs a SearXNG-style backend (`CRW_SEARCH__SEARCH_BACKEND_URL`); without one expect 503 `search_disabled`.
+
+## Limits
+
+Server defaults: 10 req/s, 60 s request timeout, 15 s search timeout. A plain `fetch` suffices; `crw-mcp` is unnecessary for search only.