[FEAT] Interactive Commit Log Selector

[xguot]

Feature Request: Interactive Commit Log Selector

Is your feature request related to a problem? Please describe.

Currently, if a user wants to diff against a specific older commit or branch, they have to manually find the Git SHA or branch name via git log and pass it as a CLI argument (e.g., difi HEAD~3 or difi 5561c25). This breaks the flow of the TUI and relies on external commands.

Describe the solution you'd like

An interactive, scrollable commit history view integrated directly into difi.

If a user runs difi --log (or presses a specific key from the empty state), they should be presented with a clean, Bubble Tea list component showing their recent Git history.

Workflow:

1. Run difi --log
2. Scroll through recent commits (j/k)
3. Press Enter on a commit
4. difi immediately opens the standard side-by-side view, diffing the working tree (or HEAD) against that selected commit.

Describe alternatives you've considered

Relying strictly on CLI arguments (difi <target>). While this is Unix-y and fast for power users who know their SHAs, it lacks the discoverability and visual ease of a TUI.

Additional context

• We can likely leverage the github.com/charmbracelet/bubbles/list component for the UI.
• It needs to support Mercurial (hg log) to maintain feature parity.
• The UI should remain minimal to match the "calm, focused" philosophy of the project.