Checks and tests run for the part a change is in

The pre-commit hook ran clippy on the whole workspace for any Rust change;
it now checks the crates touched and those built on them (ipx uses
ipx-directory, both use ipx-feed), and nothing for a change to the page
alone. CLAUDE.md says which tests go with which part.

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

CLAUDE.md

@@ -198,8 +198,18 @@ session was stopped. So:
   run in the background beside another, and never two crates' builds at once. Do not tune `-j`.
 * Look at the load before and after each (`cat /proc/loadavg`). Above about 24, Tower's twelve
   threads twice over, wait for it to come down before starting another.
-* Build only the crate the change is in (`cargo build -p ipx-directory`), and run only its tests
-  until the change is done; the whole workspace's once, at the end.
+* Test only what the change is in. ipx uses ipx-directory, and both use ipx-feed, so:
+
+  | changed | run |
+  |---|---|
+  | `web/` alone | the three page checks; `npx playwright test -g '<what changed>'`; no cargo |
+  | `crates/ipx/` | `cargo test -p ipx`; the browser tests too if the API changed |
+  | `crates/directory/` | `cargo test -p ipx-directory`, then `-p ipx` |
+  | `crates/feed/` | `cargo test -p ipx-feed`, then `-p ipx-directory`, then `-p ipx` |
+  | `Cargo.toml`, `Cargo.lock` | all three, one at a time |
+
+  The pre-commit hook's clippy follows the same table. The whole browser suite once, at the end
+  of a change to the page or the API; never `cargo test` for the workspace in one command.
 * Builds and test binaries live under `target/`, a link to `/mnt/fast`; linking through
   `/mnt/user` (FUSE) once took the load to 248 on its own.
 * **Memory is the tighter limit.** Tower has 31 GB, no swap, and the containers leave about 4-7