feat(date-time): standardize time context and tool timestamps

src/config/types.agent-defaults.ts

@@ -103,6 +103,8 @@ export type AgentDefaultsConfig = {
   bootstrapMaxChars?: number;
   /** Optional IANA timezone for the user (used in system prompt; defaults to host timezone). */
   userTimezone?: string;
+  /** Time format in system prompt: auto (OS preference), 12-hour, or 24-hour. */
+  timeFormat?: "auto" | "12" | "24";
   /** Optional display-only context window override (used for % in status UIs). */
   contextTokens?: number;
   /** Optional CLI backends for text-only fallback (claude-cli, etc.). */

src/config/zod-schema.agent-defaults.ts

@@ -41,6 +41,7 @@ export const AgentDefaultsSchema = z
     skipBootstrap: z.boolean().optional(),
     bootstrapMaxChars: z.number().int().positive().optional(),
     userTimezone: z.string().optional(),
+    timeFormat: z.union([z.literal("auto"), z.literal("12"), z.literal("24")]).optional(),
     contextTokens: z.number().int().positive().optional(),
     cliBackends: z.record(z.string(), CliBackendSchema).optional(),
     memorySearch: MemorySearchSchema,