Add git time machine for file history exploration

[patmakesapps]

Problem

Users cannot easily ask "What did this file look like 3 commits ago?" or "Show me all changes to this function in the last week."

Proposed Solution

• Wrapper around git show COMMIT:filepath
• Timeline view of file history
• Compare between commits
• Blame annotations for context

Acceptance Criteria

• Can view a file at any previous commit
• Can compare a file between two commits
• Can show change history for a specific function
• Blame annotations available