[Feature Request] Interactive Commit Graph with branch operations in Source Control

[munkgorn]

Body:

Summary

Add an interactive Commit Graph view to the Source Control panel, with common
Git branch operations available directly from the graph — similar to the
Git Graph extension for VS Code.

Motivation

Today the Source Control panel shows changes and lets me commit, but there is no
way to see the repository history as a graph. When working with multiple
branches I have to drop into a terminal (git log --graph) or a separate GUI to
understand what happened and to perform branch operations.

A built-in commit graph would keep the whole day-to-day Git workflow inside the app.

Proposed Feature

1. Commit Graph view

• Render the commit history as a graph, with one colored lane per branch.
• Show for each commit: graph node, commit subject, author, relative date, short hash.
• Show refs as labels on the commits: local branches, remote branches, tags, HEAD, stashes.
• Selecting a commit shows its details: full message, author/committer, parents,
  and the list of changed files with a diff view.
• Filter / search: by branch, by author, by message text, by commit hash.
• Lazy loading (load more commits on scroll) so large repositories stay responsive.

2. Branch operations from the graph

Right-click (context menu) on a branch label:

• Checkout branch
• Create branch (from this commit / from this branch)
• Rename branch
• Delete branch (with force option)
• Merge into current branch (with --no-ff / --squash options)
• Rebase current branch onto this branch (with interactive option if possible)
• Push / Pull / Fetch for the branch
• Set / unset upstream

Right-click on a commit:

• Checkout commit (detached HEAD)
• Create branch from this commit
• Create tag (lightweight / annotated)
• Cherry-pick commit
• Revert commit
• Reset current branch to this commit — with explicit --soft / --mixed / --hard choice
• Rebase onto this commit
• Copy commit hash / subject
• Compare with another commit / with working tree

3. Safety

• Destructive operations (reset --hard, force delete branch, force push) should
  require an explicit confirmation dialog that states exactly what will be lost.
• Show the raw Git command that will be executed, so the action is auditable.
• Surface Git errors (e.g. rebase conflicts) clearly, with a way to
  continue / skip / abort an in-progress rebase, merge, or cherry-pick.

Reference

The Git Graph extension for VS Code
(https://marketplace.visualstudio.com/items?itemName=mhutchie.git-graph)
is a good reference for both the graph rendering and the context-menu based
operations described above.

Additional context

Nice-to-have follow-ups:

• Drag-and-drop a branch label onto another branch to merge/rebase.
• Uncommitted-changes row at the top of the graph.
• Configurable graph style (colors, lane width, date format).
• Keyboard navigation through the graph.