Add git lrc stats command for review history CLI

[fuleinist]

Problem

Every git commit with git-lrc embeds review metadata in the commit message: LiveReview Pre-Commit Check: ran (iter:N, coverage:X%). However there is no way to query or visualize this history from the CLI — developers must manually parse git log to understand their review coverage over time.

Solution

Add a git lrc stats (and alias lrc stats) command that:

• Parses LiveReview Pre-Commit Check: lines from git log for the current repo
• Shows a per-repo summary: total reviewed/vouched/skipped commits, average coverage, average iterations per commit
• git lrc stats --last 30 — last N days breakdown (default: all time)
• git lrc stats --json — outputs machine-readable JSON for CI dashboards or scripting

Example output:

$ git lrc stats
Review History (all time)
✅ Reviewed : 47 commits  (avg iter: 2.3, avg coverage: 74%)
👍 Vouched  : 12 commits
⏭️ Skipped  :  5 commits
Total      : 64 commits

Example JSON output (--json):

{
  "total": 64,
  "reviewed": { "count": 47, "avg_iter": 2.3, "avg_coverage": 74 },
  "vouched": { "count": 12 },
  "skipped": { "count": 5 }
}

Use case

Developers and teams want to understand review coverage trends over time without opening the browser UI. This is especially useful for team leads tracking how well AI-generated code is being reviewed across a sprint or time period.

Scope

• Single new subcommand in cmd/stats.go (or similar)
• Reuses existing git-log parsing logic already present in the codebase
• No new API calls, no network access, no external dependencies
• Target: small, focused — no UI changes needed