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/memory/hygiene.rs

@@ -306,6 +306,8 @@ fn prune_conversation_rows(workspace_dir: &Path, retention_days: u32) -> Result<
     }
 
     let conn = Connection::open(db_path)?;
+    // Use WAL so hygiene pruning doesn't block agent reads
+    conn.execute_batch("PRAGMA journal_mode = WAL; PRAGMA synchronous = NORMAL;")?;
     let cutoff = (Local::now() - Duration::days(i64::from(retention_days))).to_rfc3339();
 
     let affected = conn.execute(

src/memory/sqlite.rs

@@ -50,6 +50,21 @@ impl SqliteMemory {
         }
 
         let conn = Connection::open(&db_path)?;
+
+        // ── Production-grade PRAGMA tuning ──────────────────────
+        // WAL mode: concurrent reads during writes, crash-safe
+        // normal sync: 2× write speed, still durable on WAL
+        // mmap 8 MB: let the OS page-cache serve hot reads
+        // cache 2 MB: keep ~500 hot pages in-process
+        // temp_store memory: temp tables never hit disk
+        conn.execute_batch(
+            "PRAGMA journal_mode = WAL;
+             PRAGMA synchronous  = NORMAL;
+             PRAGMA mmap_size    = 8388608;
+             PRAGMA cache_size   = -2000;
+             PRAGMA temp_store   = MEMORY;",
+        )?;
+
         Self::init_schema(&conn)?;
 
         Ok(Self {