docs(mcp[tools]): Search tool owns its xref anchor

[tony]

Summary

On the changelog page (/history/), the {tooliconl}search`` badge in the 0.1.0a22 entry linked to the documentation's own site-search page (/search/) instead of the MCP `search` tool reference — while the sibling `find` and `inspect_result` badges linked correctly to `/mcp/tools/#fastmcp-tool-*`. The build reported no error.

Two causes compounded:

1. The search {fastmcp-tool} card in docs/mcp/tools.md was the only one of twelve marked :no-index:, even though it is the tool's single canonical invocation. :no-index: skips registering the fastmcp-tool-search cross-reference label, so the tool had no reference home.
2. search is a Sphinx-reserved standard label (the JS "Search Page"), seeded into StandardDomain before any document is read. The tool's bare-slug alias can never claim it, so {tool}-family roles resolving by bare slug fell through to the built-in.

This PR fixes cause 1: dropping :no-index: registers the canonical fastmcp-tool-search anchor.

Dependency (why this is a draft)

Cause 2 is fixed upstream in sphinx-autodoc-fastmcp by resolving the canonical fastmcp-tool-<slug> id first: git-pull/gp-sphinx#60. Until that ships in 0.0.1a32 and this repo bumps its pin (sphinx-autodoc-fastmcp>=0.0.1a32, gp-sphinx>=0.0.1a32), the bare slug still resolves to the built-in. The pin bump + uv.lock + full completion gate will be added to this PR once a32 is released, at which point it leaves draft.

Verification

Built locally against the patched extension (gp-sphinx#60 editable): every {tooliconl}search`` on /history/ then resolves to `../mcp/tools/#fastmcp-tool-search`, matching `find` and `inspect_result`; the old `href="../search/"` tool badge is gone.

Test plan

• git diff --check clean; just build-docs succeeds; fastmcp-tool-search is now a registered std:label (/mcp/tools/#fastmcp-tool-search).
• Full completion gate runs with the a32 pin bump before this leaves draft.

Goal

Idempotent completion condition for /goal. It asserts an end state, not an action: if the state already holds, the first evaluation passes and nothing is edited.

/goal Work only in a worktree on PR #90's branch fix/mcp-search-tool-xref at the pushed PR head (the local ref is stale); never touch the shared master tree, never push. First report git rev-parse --abbrev-ref HEAD, git rev-list --count HEAD..master (23 today) and rg -c ":no-index:" docs/mcp/tools.md (0 on this branch, 1 on master, where it is the only :no-index: under docs/ and sits under the only {fastmcp-tool} search card). End state there: the branch is rebased onto local master and every MCP search tool badge on the built changelog page resolves to the tool's own anchor. Prove it by running just build-docs, then counting in docs/_build/html/history/index.html (a) badge links to ../search/ and (b) links to ../mcp/tools/#fastmcp-tool-search, and reporting both numbers: the end state is a=0 and b>0, where master today reports a=4 and b=0 - four search badges land on Sphinx's site-search page while the sibling find badge resolves correctly, silently, with no build error. Constraints: change only docs/mcp/tools.md; do not hand-write a (fastmcp-tool-search)= label, do not hard-code the resolved href into CHANGES or any other page, and do not rename, re-slug or relocate the MCP search tool - the anchor stays directive-generated so a later tools-page reorganisation still resolves. Do not touch src/agentgrep/, any other card's options, or the gp-sphinx and sphinx-autodoc-fastmcp pins: both are already 0.0.1a34, so the PR's note about waiting on gp-sphinx#60 needs no pin bump or uv.lock change. MCP behaviour is unchanged. Or stop after 6 turns and report what remains.

• Proof — git rev-parse --abbrev-ref HEAD; git rev-list --count HEAD..master; just build-docs && .venv/bin/python -c "import re,pathlib;h=pathlib.Path('docs/_build/html/history/index.html').read_text();a=len(re.findall(r'href=\"\.\./search/\"><span[^>]*gp-sphinx-fastmcp__safety',h));b=len(re.findall(r'href=\"\.\./mcp/tools/#fastmcp-tool-search\"',h));print('site-search',a,'canonical',b);raise SystemExit(0 if a==0 and b>0 else 1)"
• Idempotence — Once the branch sits on local master with the :no-index: gone, every rebuild prints site-search 0 / canonical N and the behind-count is 0, so a satisfied worktree ends on turn 1 with no edit.
• Blocked by — nothing - the pins are already at 0.0.1a34, so the PR's stale gp-sphinx#60 note imposes no prerequisite
• Blocks — nothing
• Preserves — the anchor stays directive-generated rather than hand-written, so the MCP tool slug, the tools-page layout and the set of rendered tool cards all stay free to change and a later tools-page split or tool rename still resolves; no search, cursor, ID or index contract is touched, and with no src/agentgrep change the ADR 0011 TUI pump contract is untouched