feat: add log-level system to suppress noisy fallback debug output

Replace console.debug/log/warn calls in model router, retry, and daemon
startup with a structured logger that respects a configurable log_level.
Default level is 'info', suppressing verbose fallback debug messages in
the TUI while keeping them available via config when needed.

- Add src/logger.ts with debug/info/warn/error/silent levels
- Wire log_level into config schema (default: 'info')
- Initialize log level in both daemon and TUI startup paths
- Convert all console.debug in router.ts and retry.ts to logger.debug
- Convert console.log/warn in daemon/models.ts to logger.info/warn

src/logger.ts

@@ -0,0 +1,44 @@
+/** Simple log-level utility.
+ *
+ * Default level is `info`, which suppresses `debug` output.
+ * Set to `debug` (via config or `setLevel()`) to see all messages.
+ */
+
+export type LogLevel = 'debug' | 'info' | 'warn' | 'error' | 'silent';
+
+const LEVELS: Record<LogLevel, number> = {
+  debug: 0,
+  info: 1,
+  warn: 2,
+  error: 3,
+  silent: 4,
+};
+
+let currentLevel: LogLevel = 'info';
+
+export function setLogLevel(level: LogLevel): void {
+  currentLevel = level;
+}
+
+export function getLogLevel(): LogLevel {
+  return currentLevel;
+}
+
+function shouldLog(level: LogLevel): boolean {
+  return LEVELS[level] >= LEVELS[currentLevel];
+}
+
+export const logger = {
+  debug(...args: unknown[]): void {
+    if (shouldLog('debug')) console.debug(...args);
+  },
+  info(...args: unknown[]): void {
+    if (shouldLog('info')) console.log(...args);
+  },
+  warn(...args: unknown[]): void {
+    if (shouldLog('warn')) console.warn(...args);
+  },
+  error(...args: unknown[]): void {
+    if (shouldLog('error')) console.error(...args);
+  },
+};