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/config/schema.ts

@@ -345,7 +345,10 @@ const sessionsSchema = z.object({
   ttl: z.string().default('30d'),
 }).default({});
 
+const logLevelSchema = z.enum(['debug', 'info', 'warn', 'error', 'silent']).default('info');
+
 export const configSchema = z.object({
+  log_level: logLevelSchema,
   telegram: telegramSchema,
   discord: discordSchema,
   slack: slackSchema,
@@ -406,3 +409,4 @@ export type HeartbeatCheck = z.infer<typeof heartbeatCheckSchema>;
 export type EmbeddingConfig = z.infer<typeof embeddingSchema>;
 export type EmbeddingProvider = z.infer<typeof embeddingProviderSchema>;
 export type PairingCodeConfig = z.infer<typeof pairingSchema>;
+export type LogLevel = z.infer<typeof logLevelSchema>;