Bump firewall version to v0.28.10

Update the pinned Agentic Workflow Firewall version to [`v0.28.10`](https://github.com/github/gh-aw-firewall/releases/tag/v0.28.10).

## Acceptance criteria

- All firewall version references that should track the current release use `v0.28.10`.
- Generated or locked workflow files are refreshed where applicable.
- Relevant tests and validation pass.