Add pinned Wordcell KB search with local fallback

[0thernet]

Adds pinned Wordcell 0.22.0 kb:search and kb:search:local scripts and agent guidance for ordinary repository KB searches.

Hosted search retrieves local exact candidates and reranks at most 25 with TypeSafe. Guidance identifies the transmitted fields, credential storage, diagnostic receipts, and local-only handling for confidential queries or unpublished notes. Existing SDK dependencies, lockfiles, and maintenance commands are unchanged.

Validation: reviewed immutable release; focused proposal checks preserve existing package fields and instructions; Bun argument-forwarding smoke preserves literal queries. Current-head repository CI and review gates remain pending.

[0thernet]

Reviewed during the October 1 Hraness stale-PR sweep: keep this proposal for follow-up.

No current package search script or root hosted-search guidance implements this proposal. Current KB guidance uses Wordcell, but the proposed convenient search/setup path remains absent. The v0.22 pin and paid hosted default need refresh and review; age alone does not justify closure.

Next step: Keep open for an updated pinned command and optional hosted mode, preserving applicable manifest constraints and current KB guidance.

Assessment used head 905d1f82b76f and default-branch commit dfc6340269e4. Merge readiness still needs current-head validation.

[0thernet]

Completed on current main in #260, merged as f08ac323bdc26628ae100609d4b0579f8f847ba2 after independent source review and green current-head required checks. Closing this older proposal as delivered, with the original branch and evidence preserved.