emrg: add current time + OS to system prompt (rant 2026-08-13T14:01:46)

[argszero]

Summary

Host rant 2026-08-13T14:01:46: the agent's system prompt should include current time (time awareness) and operating system (platform awareness) so it knows "what time it is now" and doesn't use wrong commands/path separators.

Changes

• emrg/server/daemon.py _build_system_prompt: adds three context fields —
  • current_time = datetime.now().astimezone().isoformat(timespec="seconds") (local tz-aware, per the established "local time, never UTC" convention)
  • os_name = platform.system() (Darwin/Windows/Linux)
  • platform_detail = platform.platform() (e.g. macOS-14.5-arm64)
• emrg/server/prompts/system.j2: renders **Current time** / **Operating system** blocks right before the Working directory line (environment info grouped together). Both gated on {% if %} so rendering stays safe.
• tests/test_daemon.py: +2 tests — rendered prompt contains tz-aware Current time + OS name; system.md debug output contains both; env info renders even without a session.
• Agent.md: Python test count 762 → 764 (doc-count guard).

Verification

• uv run pytest tests/ → 764 passed
• uv run python -c "from emrg.client.app import run_client" → OK
• uv run python -m emrg --help → OK

[argszero]

✅ LGTM — cycle

Verified locally on branch feature/system-prompt-time-os (190fed7):

• New env context fields (current_time local tz-aware ISO seconds, os_name, platform_detail) render correctly in system.j2; guarded by {% if %} so no dangling output.
• Both new tests pass: test_system_prompt_environment_time_and_os (tz-aware assertion — never naive UTC, per #556 convention) and test_system_prompt_environment_without_session (negative-state: env renders, working-dir absent).
• Full suite: 764 passed (12.95s); doc count in Agent.md updated 762→764 consistent with collect-only.
• Imports (platform, datetime) already present in daemon.py; no CI/workflow changes.
• CI (test + test-windows) still running; mergeable.

[argszero]

✅ LGTM — cycle. Env-awareness per rant 2026-08-13T14:01:46: current_time (tz-aware local ISO), os_name + platform_detail in system.j2 before Working directory; +2 tests; pytest 764 green; CI test + test-windows both pass.

[pm25coder]

I tested this PR end-to-end on the branch and it checks out:

[argszero]

✅ LGTM — cycle (3rd consecutive ✅)

Re-verified this cycle: branch head 190fed7 unchanged since prior reviews; diff vs master identical (4 files, +50/−1: Agent.md count 762→764, daemon.py env context, system.j2 guarded render, 2 new tests); full suite 764 passed locally (R1361); CI test + test-windows both PASS; mergeStateStatus CLEAN. Mergeable.