fix(team-mode): remove members from state.json on idle auto-cleanup

[Million-mo]

Problem

In team mode, when the lead goes idle for longer than idle_timeout (default 300s), the idle auto-cleanup (_schedule_member_cleanup) closes member sessions but does not remove them from state.json's members dict. Since team_add_member counts members from state.json to enforce max_members, the freed sessions still occupy capacity slots and subsequent team_add_member calls are incorrectly rejected with "Team exceeds max_members".

This means: after the lead returns from idle and tries to add new members, the old members' slots are still counted even though their sessions are gone.

Root Cause

_schedule_member_cleanup (team_comm_capability.py) closed sessions and cleared team_member_sessions metadata, but never touched state.json. Compare with _schedule_ephemeral_cleanup, which correctly pops members from state.json before closing — that path works fine.

Fix

1. _schedule_member_cleanup now accepts team_id and base_dir parameters.
2. After closing member sessions, calls new _remove_members_from_state helper that reads state.json, pops members whose session_id is in the closed set, and atomically writes back — mirroring the _schedule_ephemeral_cleanup pattern.
3. team_create passes team_id and base_dir to the cleanup scheduler.

Test

New regression test test_idle_cleanup_frees_state_json_slots_for_add_member:

• Creates a team at max_members=2 (full capacity)
• Verifies team_add_member fails before cleanup (expected)
• Triggers idle auto-cleanup (short timeouts)
• Asserts members are removed from state.json
• Asserts team_add_member succeeds after cleanup (slot freed)

All 333 existing team-mode tests + 124 delegation tests pass.

Files Changed

• src/wolfharness/capabilities/team_comm_capability.py — fix + new helper
• tests/team_mode/test_integration_session.py — regression test
• changelog/unreleased/2026-08-14-team-idle-cleanup-state-json.md — changelog