Combines the best of both open PRs, resolving their overlapping approaches
and applying all 6 fixes that are not yet in main:

**mailbox.py**
- broadcast(): resolve logical agent names to inbox directory names before
  exclusion check, so the sender is not delivered their own broadcast when
  inboxes use user-prefixed format (e.g. "alice_worker" vs "worker")
  [from PR HKUDS#15]
- receive() / peek(): replace bare list comprehension with _parse_messages()
  helper that wraps each message in try/except, so a single corrupted file
  no longer crashes the entire fetch [from PR HKUDS#9]

**transport/file.py**
- fetch(consume=True): atomically rename msg file to .consumed before
  reading, so concurrent callers cannot both receive the same message
  [from PR HKUDS#15]

**cli/commands.py**
- config set / config get: derive valid_keys from ClawTeamConfig.model_fields
  instead of a hardcoded 3-item set, making all 7 config keys accessible;
  handle boolean fields (skip_permissions) correctly [from PR HKUDS#15]
- approve-join: return an error and exit(1) when no matching join request
  is found, instead of silently fabricating an agent name [from PR HKUDS#9]
- launch_team: read skip_permissions from config and pass it to be.spawn(),
  matching the behaviour of the standalone spawn command [from PR HKUDS#15]

Note: the plans-cleanup fix (PR HKUDS#9 subdirectory approach, PR HKUDS#15 member-filter
approach) was already merged via PR HKUDS#6 using the subdirectory strategy, so it
is intentionally excluded here.

All 135 existing tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Covers:
- Task 2 core: safety subscriber registration, start_sprint state.json + event emit,
  gate chain order + short-circuit, auto_advance semantics (4 combinations),
  MissingTeamError, resolve_sprint prefix/ambiguous/not-found, list_sprints
  team-scoped (Pitfall HKUDS#9), three-layer cap override (D-29), advance_phase happy-path
- Task 3 pause/resume: in-process round-trip, cross-subprocess restart (CORE-07),
  last PhaseTransition re-emit on resume, careful_enabled restoration on resume

- Register sprint_app = typer.Typer(...) via app.add_typer(name='sprint').
- Ship 6 sub-commands: start, status, show, list, pause, resume — each
  dispatches into SprintConductor and owns error-to-envelope translation.
- Add _sprint_emit_ok / _sprint_emit_err helpers emitting the uniform
  {ok, data, warnings, error} envelope per D-26 (mirrors guard_app pattern).
- Add _resolve_team_arg (Pitfall HKUDS#9: MISSING_TEAM when --team + env absent)
  and _resolve_sprint_or_err (translates AmbiguousSprintError /
  SprintNotFoundError → AMBIGUOUS_SPRINT / SPRINT_NOT_FOUND codes).
- CLI flags --artifact-cap / --phase-artifact-cap honor the three-layer D-29
  override; --auto-advance/--no-auto-advance toggles INT-06 semantics.
- Human renderer uses existing module-level rich console (BC-preserving).
- Close UX-02 (start), UX-03 (status), UX-04 (list), UX-05 (show), UX-09
  (uniform JSON envelope across all 6 commands).
- 15 CliRunner tests cover success + error-code branches; Phase 0 regression
  matrix 12/12 stays green (sub-app is additive, no existing command edits).