ci(release): use app token for release PR updates

[bokelley]

Summary\n- mint an IPR GitHub App installation token in the Release Please workflow\n- pass that token to release-please-action so release PR branch updates trigger downstream protected checks\n- use the same token for the pyproject prerelease normalization checkout/push\n\n## Why\nRelease Please was using the default GITHUB_TOKEN. Branches updated with GITHUB_TOKEN do not trigger pull_request CI/IPR workflows, so generated release PRs could be green for CodeQL/GitGuardian but blocked waiting for required CI contexts that never ran.\n\n## Validation\n- uv run --extra dev --group dev pre-commit run --files .github/workflows/release-please.yml

[aao-ipr-bot]

LGTM. Right diagnosis, right fix: GITHUB_TOKEN-authored pushes don't trigger downstream pull_request workflows, so release-please PRs were sitting blocked on required contexts that never started. Threading an App installation token through both the action and the pre-normalize checkout is the documented escape hatch.

Things I checked

• Token flows through both the release-please-action step (release-please.yml:26) and the pre-normalize actions/checkout@v6 (release-please.yml:34) — the two paths that actually push to the release PR branch.
• Second checkout for the PyPI publish path (release-please.yml:71) intentionally uses the default token. Fine — it only reads, never pushes.
• Workflow-level permissions: block (release-please.yml:14-16) is unchanged and still correct; the App's own installation permissions are what governs the release-please push now.
• Commit message uses ci(release): — no semver impact, matches conventional-commits.
• src/ and tests are untouched; no public API surface to audit.

Follow-ups (non-blocking — file as issues)

• Verified-bot commit email format. release-please.yml:75-76 sets aao-ipr-bot[bot]@users.noreply.github.com. For the commit to verify against the App's identity, the noreply form needs the numeric-ID prefix: <APP_USER_ID>+aao-ipr-bot[bot]@users.noreply.github.com (mirrors the previous 41898282+github-actions[bot]@… shape). Without the prefix, normalize commits will show as unverified. The numeric ID is on GET /users/aao-ipr-bot%5Bbot%5D.
• Undocumented IPR_APP_ID / IPR_APP_PRIVATE_KEY for forks. RELEASING.md and PYPI_SETUP.md only mention PYPY_API_TOKEN. A fork that copies this workflow will hit an opaque create-github-app-token failure at the Mint App token step. Either add an App-setup section to RELEASING.md or fall back to GITHUB_TOKEN when the secret is empty (if: \${{ secrets.IPR_APP_ID != '' }} on the mint step + conditional token: inputs). Falls under the same documented pattern as ai-review.yml / ipr-agreement.yml.
• Normalize step gates on prs_created == 'true' (release-please.yml:36). A subsequent push to main that updates an existing release PR will set prs_updated, not prs_created, and the normalization will be skipped. release-please regenerates pyproject.toml on updates, so the unnormalized version can land on the PR until the next created-cycle. Consider widening the gate to also cover prs_updated.
• Branch-protection allowlists. Identity flip from github-actions[bot] to aao-ipr-bot[bot] will fail-closed if any "Restrict who can push" list on main or the release branch still names only the old identity. Can't verify from the tree — confirm in repo settings before this merges into production traffic.

Minor nits (non-blocking)

1. Unused mint on publish-only dispatch. Mint App token (release-please.yml:25) runs unconditionally, but the next step is gated by if: github.event_name != 'workflow_dispatch' || inputs.publish != true. On a publish-only workflow_dispatch, the token is issued and never used. Mirror the same if: on the mint step if you want to skip the wasted issuance.

Approving on the strength of the token threading and the unchanged publish path. Verified-commit email is the one that's worth a quick follow-up.