fix: pass host timezone to container and reject UTC-suffixed timestamps (#371)

Containers had no TZ set, so any time-aware code inside ran in UTC while
the host interpreted bare timestamps as local time. Now TIMEZONE from
config.ts is passed via -e TZ= to the container args.

Also rejects Z-suffixed or offset-suffixed timestamps in the container's
schedule_task validation, since bare timestamps are expected to be local
time and silently accepting UTC suffixes would cause an offset mismatch.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/container-runner.ts

@@ -13,6 +13,7 @@ import {
   DATA_DIR,
   GROUPS_DIR,
   IDLE_TIMEOUT,
+  TIMEZONE,
 } from './config.js';
 import { readEnvFile } from './env.js';
 import { resolveGroupFolderPath, resolveGroupIpcPath } from './group-folder.js';
@@ -187,6 +188,9 @@ function readSecrets(): Record<string, string> {
 function buildContainerArgs(mounts: VolumeMount[], containerName: string): string[] {
   const args: string[] = ['run', '-i', '--rm', '--name', containerName];
 
+  // Pass host timezone so container's local time matches the user's
+  args.push('-e', `TZ=${TIMEZONE}`);
+
   // Run as host user so bind-mounted files are accessible.
   // Skip when running as root (uid 0), as the container's node user (uid 1000),
   // or when getuid is unavailable (native Windows without WSL).