What does this PR do?

When a user configured a timezone (HERMES_TIMEZONE env var or timezone: key
in ~/.hermes/config.yaml), the agent didn't know about it. Two visible symptoms:

1. The system prompt's timestamp had no zone marker, so the model fell back to
   server-local time. "What's today's date?" returned the server's date, not
   the user's.
2. date (and any TZ-honouring runtime) inside the terminal tool reported the
   server's wall clock, so shell output disagreed with what the agent thought
   the time was.

Fixed end-to-end via two centralized injection points instead of touching each
backend individually:

• Agent prompt (run_agent.py): append a Timezone: <IANA> (UTC±HH:MM)
  line to the timestamp block when a timezone is configured.
• Every terminal backend: BaseEnvironment._wrap_command injects
  export TZ=<name> once. That covers local, docker, ssh, singularity, modal,
  and daytona — all six flow through this method. Managed Modal uses a different
  exec path (BaseModalExecutionEnvironment._prepare_modal_exec), so it gets
  the same injection there.
• Resolver (tools/environments/base.py): new _resolve_configured_tz_name()
  reads via hermes_time.get_timezone(), which checks both HERMES_TIMEZONE
  and ~/.hermes/config.yaml. CLI entry points like hermes chat don't bridge
  config.yaml → env var (only gateway/run.py does), so an env-var-only check
  would silently miss config.yaml-only setups. This resolver covers them.

Related Issue

N/A — no existing issue. Reproduced locally with timezone: Asia/Shanghai in
~/.hermes/config.yaml running on a UTC server.

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• run_agent.py — emit Timezone: <IANA> (UTC±HH:MM) after the timestamp when
  configured. Uses hermes_time.now() so the offset is computed in the user's
  zone.
• tools/environments/base.py — new _resolve_configured_tz_name() helper;
  BaseEnvironment._wrap_command injects export TZ=<name> after the snapshot
  source so it overrides anything inherited.
• tools/environments/modal_utils.py —
  BaseModalExecutionEnvironment._prepare_modal_exec prepends
  export TZ=<name>; after sudo wrapping (covers ManagedModalEnvironment).
• tools/environments/local.py — _make_run_env and _sanitize_subprocess_env
  set TZ=<name> on the subprocess env so PTY/background terminals (spawned
  via process_registry.spawn_local) and the init_session bootstrap that
  runs before the snapshot exists also agree. Refactored to use the shared
  helper.
• Tests:
  • tests/run_agent/test_run_agent.py — test_includes_timezone_when_configured,
    test_omits_timezone_line_without_config.
  • tests/tools/test_base_environment.py — TestWrapCommandTimezone (4) and
    TestResolveConfiguredTzName (3).
  • tests/tools/test_modal_utils_tz.py — TestPrepareModalExecTimezone (4)
    [new file].
  • tests/tools/test_local_env_blocklist.py — TestTimezonePropagation (5).

How to Test

1. Set timezone (pick one):
   • export HERMES_TIMEZONE=Asia/Shanghai, or
   • Add timezone: Asia/Shanghai to ~/.hermes/config.yaml (with no
     HERMES_TIMEZONE env var).
2. Start hermes chat. The system prompt should include
   Timezone: Asia/Shanghai (UTC+08:00) right under the timestamp.
3. In the chat, ask the agent to run date. Output should be Asia/Shanghai
   wall-clock time (CST), not the server's zone.
4. Targeted unit tests:

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix: prefix; one squashed commit)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix (one squashed commit, eight files)
• I've run pytest on the affected modules and all tests pass (301 passed); full pytest tests/ not re-run end-to-end
• I've added tests for my changes
• I've tested on my platform: macOS 15 (Darwin 25.4.0)

Documentation & Housekeeping

• I've updated relevant documentation — not done. Timezone configuration
  is currently undocumented anywhere on https://hermes-agent.nousresearch.com/docs
  (verified via the docs search). Worth a follow-up doc PR; this PR keeps
  its surface area to the bug.
• I've updated cli-config.yaml.example if I added/changed config keys —
  N/A: no new config keys; the existing timezone key just starts
  working in places where it was silently ignored.
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture
  or workflows — N/A: no architecture changes.
• I've considered cross-platform impact — export TZ=<name> is POSIX; the
  change works on Linux, macOS, Termux, and Git Bash on Windows since every
  terminal backend already shells through bash.
• I've updated tool descriptions/schemas if I changed tool behavior —
  N/A: no tool schema or description changes.