chore(changeset): add pr: 3216 to build-hooks-atomic-write changeset

The changeset parser hard-fails on fragments without a pr: field.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.changeset/build-hooks-atomic-write.md

@@ -1,4 +1,5 @@
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 type: Fixed
+pr: 3216
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 **Atomic writes in `scripts/build-hooks.js` to fix flaky release CI** — nine test files invoke `build-hooks.js` from their `before()` hooks, and `scripts/run-tests.cjs` runs test files with `--test-concurrency=4`, so multiple builders raced to rewrite the same files in `hooks/dist/`. `fs.copyFileSync(src, dest)` truncates `dest` then writes it; a parallel `bin/install.js` subprocess (spawned by another install test) could `fs.readFileSync` between the truncate and the write and observe an empty file. install.js then wrote that empty content into the install target, so installed `.sh` hooks lacked their `# gsd-hook-version:` header. This surfaced as the release-blocking failure in `tests/bug-2136-sh-hook-version.test.cjs` part 4 even though the same SHA passed on every other Node-22/Node-24 install-smoke matrix run. `build-hooks.js` now stages each output to a sibling `hooks/.dist-staging/` directory (same filesystem as `hooks/dist/`) and uses `fs.renameSync` to swap into place — POSIX `rename(2)` is atomic, so concurrent readers always observe a complete file. The existing `tests/bug-2136-sh-hook-version.test.cjs` part 4 already locks the post-fix invariant. (Failing run: https://github.com/gsd-build/get-shit-done/actions/runs/25472202941/job/74738276687)