Let github_pulls find open PRs that touch a path

• Status: Todo
• Kind: Feature
• Authors: jp
• Date: 2026-10-01
• Label: domain=tooling

github_pulls lists pull requests by state only (.config/jp/tools/src/github/pulls.rs, list). github_code_search searches the default branch only, so code that exists only in an open PR is invisible to it. Answering "which open PR adds crates/jp_process?" takes one github_pr_diff call per open PR, and an assistant that skips some of them answers wrong.

That happened during T-0vm44ks: the search covered the code index and one PR's file list, found nothing, and reported that no shared process runner existed. PR #1175 added it. The user found it with a shell loop over gh api repos/dcdpr/jp/pulls/$n/files.

Fix: add an optional path parameter to github_pulls, a path prefix. With it set, the tool lists the PRs matching state and keeps those whose changed files include a path under the prefix, naming the matching files for each. The file lists are paginated (100 per page, up to 3000 files), so every page is read; a PR with more files than the API returns says so rather than being reported as a non-match.

Test with a mocked client: two open PRs, one touching crates/jp_process/src/lib.rs, filtered on crates/jp_process, returns only that PR and that file.