chore: allow release-please workflow to be run via workflow_dispatch

[tanderson-ld]

Summary

• Add workflow_dispatch: to .github/workflows/release-please.yml so the release-please workflow can be re-fired manually from the Actions UI without pushing a commit to main.

Motivation

When a commit lands on main whose message release-please can't parse (e.g. run 29123151878, where the squash-merge body of PR #324 tripped the conventional-commits parser), the workflow completes without opening a release PR. Recovering currently requires either editing the offending PR body (to add a BEGIN_COMMIT_OVERRIDE block) and then pushing another commit to main to retrigger, or landing a follow-up commit whose sole purpose is to fire the workflow. Adding workflow_dispatch lets us edit the PR body and click "Run workflow" from the Actions UI instead.

Test plan

• After merge, the release-please workflow appears in the Actions UI with a "Run workflow" button on the main branch and re-runs cleanly on demand.

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Note

Low Risk
Single trigger addition on an existing release automation workflow; no change to release-please steps, permissions, or publishing behavior.

Overview
Adds workflow_dispatch to release-please.yml, so release-please can be started from the GitHub Actions UI in addition to pushes to main.

This supports recovery when a main push does not produce a release PR (for example, a squash-merge message that release-please cannot parse). After fixing the PR body or related metadata, you can re-run the workflow without pushing a no-op commit to main.

^{Reviewed by Cursor Bugbot for commit 90555f6. Bugbot is set up for automated code reviews on this repo. Configure here.}