Run jp wiki check in CI against JP's own wiki

Todo2026-11-01jp

domain: toolingrelevant-rfd: 127type: task

Nothing in CI runs jp wiki check against JP's wiki. RFD 127 asks for jp wiki check to run on every pull request that could break a page, including ones that only change source, since pages link to line ranges in source files.

Running it needs jp: the plugin gets the workspace root and the resolved, layered configuration (the wiki, RFD, and ticket directories, the repository address) from the host, and building jp in CI only to run one check is expensive. A standalone mode that reads .jp/config.toml itself was ruled out: it would load configuration differently from jp.

Two ways forward:

• Once jp has binary releases (RFD 123), CI downloads a released jp, builds only jp-wiki, and runs jp wiki check --strict.
• Config loading moves into a small helper that a plugin, or a CI job, can run without the whole of jp.

The job needs full git history, since permalinks are checked against the default branch, and has to run on source changes, not only on docs/.

Until then, jp_wiki_passes_check in crates/plugins/command/wiki runs the check over JP's wiki as part of cargo test, reading .jp/config.toml as plain TOML. Remove it once CI runs the real command.