Step 6: control socket and daemon

Unix-socket JSON-lines protocol replacing the printMSG sentinels, with
an Emitter so scan code is agnostic about whether a terminal or a UI is
watching. Daemon serves clients and runs a TTL-aware scheduler; commands
funnel through one worker so scans cannot overlap, and the CLI proxies to
a running daemon rather than competing with it.

The pre-fetch retention sweep was emitting the terminal ReapDone event,
which would have ended a client's read before the scan began.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RPyeapneuXrCdojsaiXGbe

src/db.rs

@@ -385,6 +385,17 @@ impl Db {
     }
 }
 
+impl Db {
+    /// (pending, downloaded) across all feeds, for the status command.
+    pub fn counts(&self) -> Result<(i64, i64)> {
+        let conn = self.conn.lock().unwrap();
+        Ok((
+            conn.query_row("SELECT count(*) FROM enclosures WHERE state = 'pending'", [], |r| r.get(0))?,
+            conn.query_row("SELECT count(*) FROM enclosures WHERE path IS NOT NULL", [], |r| r.get(0))?,
+        ))
+    }
+}
+
 /// Unix seconds. Everything time-shaped in the DB is stored this way.
 pub fn now() -> i64 {
     std::time::SystemTime::now()