fix(release): fetch draft-notes PR summaries in batches (#20602)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - The release workflow drafts the next stable's release notes when a
beta publishes (`draft_stable_notes`)
> - The draft nests each referenced PR's summary under its commit
subject, and it fetches each summary with its own `gh pr view` call
> - A beta range now references more than 1,500 PRs, so these serial
calls do not finish inside the job's 10-minute timeout
> - This pull request fetches the summaries in batches of 50 per GraphQL
query
> - The benefit is that the job finishes in under a minute and pushes
the notes branch again

## Linked Issues or Issue Description

**What happened?**

The `draft_stable_notes` job of [run
42763789753](https://github.com/paperclipai/paperclip/actions/runs/42763789753)
(beta `2026.1110.0-beta.0`) reached its 10-minute timeout. GitHub
cancelled it during "Draft stable notes from the published beta", while
a `gh` process was still running. The beta itself published and its
smoke tests passed. The `release-notes/v2026.1110.0-beta.0` branch was
not pushed.

**Expected behavior**

The job writes the notes draft and pushes the branch for every beta,
whatever the size of the commit range.

**Steps to reproduce**

1. Publish a beta whose range from the last stable has many
PR-referencing commits. This range has 1,586 commits, and 1,583
different PRs.
2. `draft-stable-notes.sh` calls `gh pr view <n>` once for each commit,
one after another.
3. The job reaches `timeout-minutes: 10` before the loop ends.

**Paperclip version or commit**

`09e24dd12c36251dd12af2d73dbc715ce990f922` (beta `2026.1110.0-beta.0`).
This was the first beta to run the job after #12124 added the PR
summaries; earlier betas skipped it.

## What Changed

- `scripts/draft-stable-notes.sh`:
- Collects the unique PR numbers first. Fetches their bodies 50 per `gh
api graphql` query (aliased `pullRequest(number:)` fields), into a
temporary cache that `enrich_pr` reads.
- Parses the raw response with `jq`, not with `gh --jq`. When any number
in a batch is not a PR (for example, an issue reference), gh exits
non-zero and does not apply its `--jq` filter. The other PRs in the
batch still have usable data.
- The output format does not change. A missing `gh` or `jq`, a failed
batch, a cache directory that `mktemp` cannot create, or
`DRAFT_NOTES_SKIP_PR_ENRICHMENT=1` still gives bare subjects.
- No code comments are added (per `CONTRIBUTING.md`); this description
holds the explanation.
- `scripts/draft-stable-notes.test.mjs`:
- The enrichment tests now use a fake `gh` that answers GraphQL like
GitHub.
- New tests: batching (120 PRs make 3 queries, and a repeated PR is
fetched once); a batch with a non-PR number; a failed batch; a failed
`mktemp`; prose-only and empty bodies; the opt-out.
- Range tests now run with enrichment disabled, so an authenticated `gh`
on the test machine cannot reach GitHub.
- `package.json`: adds the test file to `test:release-registry`. These
tests did not run in CI before.

## Verification

- `node --test scripts/draft-stable-notes.test.mjs`: 17 pass. They also
pass with macOS bash 3.2 first on `PATH`.
- `node scripts/ci-profile/node-test.mjs
scripts/draft-stable-notes.test.mjs scripts/release-lib.test.mjs`: 31
pass.
- Red check: the new tests against the old script fail 5 cases (all
batching and enrichment cases). The `mktemp` test fails against an
unguarded `mktemp` call.
- Live run on the real range: `./scripts/draft-stable-notes.sh
2026.1110.0-beta.0` finished in 47 seconds. It wrote 4,596 excerpt lines
for 1,583 PRs.
- Parity: for 40 randomly sampled PRs from that range, the new excerpts
are byte-identical to the old per-PR `gh pr view` output.
- `shellcheck`: no new findings. The two remaining notices were there
before this change.

## Risks

- Low. The change touches only the post-publish draft job, and every
failure still gives the bare-subject draft.
- `jq` is now needed for the PR summaries. GitHub's Ubuntu runners
include it. Without `jq`, the draft has no summaries, the same as
without `gh`.
- I did not change `release.yml`. The job already checks out `master`,
so after this merges, re-running the failed job of run 42763789753
should push the missing notes branch with the fixed script.

## Model Used

- Claude Opus 5.5 (`claude-opus-5-5`) via Claude Code, with tool use
(shell, file editing, test runs, read-only GitHub API calls).

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

---------

Co-authored-by: Paperclip <noreply@paperclip.ing>

scripts/draft-stable-notes.sh

@@ -129,10 +129,47 @@ subjects="$(git -C "$repo_dir" log --no-merges --format='%s' "$range")"
 # "What Changed" bullets, falls back to the first prose lines. Degrades
 # silently when gh or the network is unavailable (tests, offline runs);
 # set DRAFT_NOTES_SKIP_PR_ENRICHMENT=1 to disable explicitly.
+PR_BATCH_SIZE=50
+pr_cache=""
+
+fetch_pr_batch() {
+  local query="query(\$owner: String!, \$name: String!) { repository(owner: \$owner, name: \$name) {" pr_num num encoded
+  for pr_num in "$@"; do
+    query+=" pr${pr_num}: pullRequest(number: ${pr_num}) { body }"
+  done
+  query+=" } }"
+  (cd "$repo_dir" && gh api graphql -F owner='{owner}' -F name='{repo}' -f query="$query" 2>/dev/null) \
+    > "$pr_cache/batch.json" || true
+  while IFS=$'\t' read -r num encoded; do
+    [[ "$num" =~ ^[0-9]+$ ]] || continue
+    printf '%s' "$encoded" | base64 -d > "$pr_cache/$num" 2>/dev/null || rm -f "$pr_cache/$num"
+  done < <(jq -r '.data.repository // {} | to_entries[]
+      | select((.value | type) == "object" and (.value.body | type) == "string")
+      | "\(.key | ltrimstr("pr"))\t\(.value.body | @base64)"' "$pr_cache/batch.json" 2>/dev/null || true)
+}
+
+prefetch_pr_bodies() {
+  local pr_nums=() pr_num
+  [ "${DRAFT_NOTES_SKIP_PR_ENRICHMENT:-0}" = "1" ] && return 0
+  command -v gh >/dev/null 2>&1 || return 0
+  command -v jq >/dev/null 2>&1 || return 0
+  while IFS= read -r pr_num; do
+    [ -n "$pr_num" ] && pr_nums+=("$pr_num")
+  done < <(printf '%s\n' "$subjects" | grep -oE '\(#[0-9]+\)$' | tr -dc '0-9\n' | sort -un || true)
+  [ "${#pr_nums[@]}" -gt 0 ] || return 0
+  pr_cache="$(mktemp -d)" || { pr_cache=""; return 0; }
+  trap 'rm -rf "$pr_cache"' EXIT
+  local start=0
+  while [ "$start" -lt "${#pr_nums[@]}" ]; do
+    fetch_pr_batch "${pr_nums[@]:$start:$PR_BATCH_SIZE}"
+    start=$((start + PR_BATCH_SIZE))
+  done
+}
+
 enrich_pr() {
   local pr_num="$1" pr_body excerpt
-  [ "${DRAFT_NOTES_SKIP_PR_ENRICHMENT:-0}" = "1" ] && return 0
-  pr_body="$(cd "$repo_dir" && gh pr view "$pr_num" --json body --jq .body 2>/dev/null || true)"
+  [ -n "$pr_cache" ] && [ -s "$pr_cache/$pr_num" ] || return 0
+  pr_body="$(cat "$pr_cache/$pr_num")"
   [ -n "$pr_body" ] || return 0
   if printf '%s\n' "$pr_body" | grep -q '^## What Changed'; then
     excerpt="$(printf '%s\n' "$pr_body" | sed -n '/^## What Changed/,/^## /p' | grep -E '^- ' | head -3 || true)"
@@ -163,6 +200,8 @@ section() {
   printf '\n'
 }
 
+prefetch_pr_bodies
+
 conventional='^(feat|fix)(\([^)]*\))?!?: '
 mkdir -p "$(dirname "$out_file")"
 {