fix(tui): show log timestamps on the viewer's local clock

[mkonopelski-gd]

Summary

TUI timestamps were rendered as raw UTC wall-clock time, so an event that happened at 17:24 local (CEST) showed up as 15:24:… in the message feed. The session list was worse — it explicitly called .astimezone(timezone.utc) on created_at before formatting, pinning the list to UTC no matter where the user sits.

Every timestamp the TUI renders now shows on the viewer's local clock, and no UTC clock time reaches the TUI at all.

Entrypoint

mcp_server/tui/render.py — format_local() replaces the private _hhmmss() helper and is the single place the TUI turns a backend ISO timestamp into a displayable clock time.

Details

• render.format_local(timestamp, fmt=LOCAL_TIME_FORMAT) parses the ISO value, treats an offset-naive value as UTC (so a clock time is never shifted twice), then formats in the process-local zone. Returns "" for missing/unparseable input, as before.
• Live message feed (stream_row) and agent error/warning rows (agent_error_event_rows) both go through it — same call sites as the old helper, now local.
• Session list (_session_label in app.py) reuses the same function with LOCAL_DATE_TIME_FORMAT instead of its own fromisoformat().astimezone(timezone.utc).strftime(); the raw-prefix fallback for unparseable values is kept. datetime/timezone imports dropped from app.py.
• Retry stream line (claude_code.py) no longer spells out next attempt at 15:26 UTC. It was the last absolute clock time reaching the TUI, sitting right next to a local-clock timestamp. Converting it server-side is not an option: the backend runs in a container whose zone is UTC regardless of the host, so astimezone() there prints the same digits with the label removed. The relative wait (waiting 2m 0s before retry (crash 2/6)) needs no timezone, and the absolute instant remains on the event's structured next_attempt_at field if the TUI ever wants to render it locally.
• Backend server logs keep their explicit UTC label — they are not TUI surfaces (the Recent activity log tail that would show them is currently disabled in build_dashboard).

Tests

New mcp_server/tests/conftest.py exposes a local_timezone fixture (context-manager factory pinning TZ + time.tzset()) so local-time assertions are deterministic instead of machine-dependent.

• TestFormatLocal: UTC → local conversion, offset-naive read as UTC, non-UTC offset input, day rollover in the date format, blank/unparseable input.
• Existing stream-row and error-row time assertions updated to the local-clock contract (14:02:31Z → 16:02:31 in Europe/Warsaw).
• _session_label: created_at shown in local time, plus the unparseable fallback.

make unit-tests → 702 MCP-server tests + full backend suite pass.