feat: add Git operations tool for structured repository management

Implements #214 - Add git_operations tool that provides safe, parsed
git operations with JSON output and security policy integration.

Features:
- Operations: status, diff, log, branch, commit, add, checkout, stash
- Structured JSON output (parsed status, diff hunks, commit history)
- SecurityPolicy integration with autonomy-aware controls
- Command injection protection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cron/mod.rs

@@ -255,6 +255,16 @@ fn with_connection<T>(config: &Config, f: impl FnOnce(&Connection) -> Result<T>)
     let conn = Connection::open(&db_path)
         .with_context(|| format!("Failed to open cron DB: {}", db_path.display()))?;
 
+    // ── Production-grade PRAGMA tuning ──────────────────────
+    conn.execute_batch(
+        "PRAGMA journal_mode = WAL;
+         PRAGMA synchronous  = NORMAL;
+         PRAGMA mmap_size    = 8388608;
+         PRAGMA cache_size   = -2000;
+         PRAGMA temp_store   = MEMORY;",
+    )
+    .context("Failed to set cron DB PRAGMAs")?;
+
     conn.execute_batch(
         "CREATE TABLE IF NOT EXISTS cron_jobs (
             id          TEXT PRIMARY KEY,