Surface and control commit signing when committing from the Commit Graph

[ianhattendorf]

Summary

When committing working changes from the Commit Graph's commit box, GitLens should make commit signing visible and honor VS Code's git.enableCommitSigning setting — showing whether the commit will be signed and with what format.

Background

• Commits made from the Commit Graph only sign when the repo's commit.gpgsign Git config is set. Users who enable signing solely through VS Code's git.enableCommitSigning (the way the built-in Source Control signs) get unsigned commits from the Graph. Standalone-packages refactor dropped host-config wiring (force-push, similarity threshold, commit signing settings ignored) #5326 corrected how the signing config is reported and fixed the Compose path, but the direct working-changes commit path still doesn't honor the setting.
• There is no feedback in the commit box about whether a commit will be signed — users only learn afterward (signature badges) or when signing fails.

Proposed behavior

1. Commits from the Commit Graph commit box honor git.enableCommitSigning, matching the built-in Source Control behavior.
2. A signing indicator (key icon) appears in the commit box when commits will be signed, showing the format (GPG, SSH, X.509, or OpenPGP) on hover.

Impact

• Users who sign via the VS Code setting get correctly-signed Graph commits, consistent with the SCM.
• Clear, upfront feedback about signing state before committing.

Validation

• With git.enableCommitSigning on (no commit.gpgsign), commit from the Graph → commit is signed.
• Key indicator appears with the correct format label when signing is enabled; removed when disabled.