feat(web): add Git History to the repository workspace

[Defmon3]

Important

This PR is stacked on pingdotgg/t3code#6315 and targets Bil0000:feat/issues-page.

Why

PR pingdotgg#6315 adds provider-neutral Issues and improves the relationship between issues and pull requests. Repository history is still separate from those workflows.

This adds Git History as the third Repository view so history, issues, and pull requests share one project-scoped workspace.

What changed

• Adds provider-neutral Git history contracts and bounded server operations for commits, refs, commit details, changed files, and diffs.
• Adds a responsive History view with a commit graph, branches and tags, commit details, file pagination, and diff navigation.
• Integrates History, Issues, and Pull Requests into the same Repository panel while preserving project and environment context.
• Keeps selected refs, commit state, and repository routing stable across reconnects and responsive layout changes.
• Reuses the existing Issues and Pull Requests views without changing their established workflows.

Performance and limits

• Commit, ref, and changed-file pagination is bounded.
• Large ref enumeration is streamed instead of retained as one complete stdout payload.
• Cursor snapshots expire and are invalidated by repository mutations.
• Search does not automatically page through every result.
• ResizeObserver notifications only update React state when the layout breakpoint or pane bounds actually change.

Compatibility

• Existing Issues and Pull Requests routes remain available.
• Unsupported Git History environments show a capability message.
• Repository behavior remains scoped by environment and project.
• No new dependencies were added.

Verification

• Focused History, server, client-runtime, and contract tests passed.
• Scoped lint and formatting passed for the changed files.
• Independent correctness and performance reviews completed.
• Live web verification covered Repository tab switching, the full three-pane History layout, commit selection and details, and the existing Issues and Pull Requests views.

UI

History

Issues

Pull Requests

Built with GPT-5.6 Codex in T3 Code.

[Defmon3]

Superseded by this four-part review series, reviewed in order:

1. Server API, based directly on feat/issues-page at 3033fdac0.
2. History client.
3. Repository pane.
4. Issues integration.

Each replacement contains one incremental commit. Parts 2–4 target the preceding branch in my fork because I cannot create base branches in Bilal's fork. Each cumulative layer was verified on an isolated dev server.

Closing this combined proposal to keep review in one place. Its description, original images, branch and discussion remain preserved. The replacements link back here. Current interaction demo.