Add unsigned retry for commit signing failures

[tim-smart]

Summary

• Detect commit signing failures and expose a one-time unsigned retry for web and mobile Git actions.
• Preserve feature-branch state during retries and pass --no-gpg-sign only for the retried commit.
• Improve commit hook progress ordering and output attribution while avoiding leaked signing diagnostics.
• Clear stale toast actions while Git operations are running.
• Add contract, client-runtime, VCS, and Git manager coverage for signing failures and retry behavior.

Testing

• Not run (PR content generated from the provided diff).
• Added focused tests for signing-failure classification, unsigned commits, feature-branch retries, hook failures, progress ordering, and hook-output attribution.