fix(tests): catch up 25 stale tests after recent merges (#28626)

Sweep of all CI failures on origin/main, grouped by drift source:

Telegram allowlist gate (db50af910 added user-authz to _should_process_message):
- Hardcoded "[Telegram]" prefix in the logger.warning so the call no
  longer dereferences self.name → self.platform, which test fixtures
  built via object.__new__ never set.
- test_telegram_format / test_allowed_channels_widening fixtures stub
  _is_callback_user_authorized → True so the new gate doesn't reject
  guest-mode / allowed-channels test messages.
- test_telegram_approval_buttons::test_update_prompt_callback_not_affected
  sets TELEGRAM_ALLOWED_USERS="*" so the fail-closed default doesn't
  reject the callback before it writes .update_response.

Approval surface (6d495d9e7 renamed status, 214b95392 detached stdin):
- test_no_callback_returns_approval_required: status is now
  "pending_approval" (was "approval_required").
- test_close_stdin_allows_eof_driven_process_to_finish: switch to
  use_pty=True; non-PTY now uses stdin=DEVNULL.

Mattermost (send() now resolves root_id via _api_get first):
- test_send_with_thread_reply mocks _session.get with a thread-root
  response so the new resolver doesn't TypeError on a bare AsyncMock.

Kanban (d8ad431de rename, f55d94a1e review column, _kanban_worker_skill_available):
- _safe_int → _to_epoch in the two test_kanban_db tests.
- Spawn-skills tests (×3) monkey-patch _kanban_worker_skill_available
  to True since the isolated kanban_home fixture has no devops/kanban-worker tree.
- test_gateway_dispatcher_disables_corrupt_board: connect count
  3 → 5 (review-column probe now also runs per tick).

Aux-config severity at_or_above (a94ddd807):
- test_diagnostics_endpoint_severity_filter expects warning filter to
  include error+critical now (was exact-match).

Anthropic error handling (conversation loop extracted from run_agent):
- _no_backoff_wait fixture patches BOTH run_agent.jittered_backoff AND
  agent.conversation_loop.jittered_backoff. The latter is the actual
  call site; without the second patch tests burn ~2s per retry and
  hit the 30s SIGALRM timeout on CI.

Other test pollution / drift:
- test_auto_does_not_select_copilot_from_github_token: patch
  agent.bedrock_adapter.has_aws_credentials → False so boto3's
  credential chain can't auto-pick Bedrock from developer ~/.aws.
- test_setup_openclaw_migration: patch hermes_cli.gateway.get_env_value
  in addition to setup_mod.get_env_value — _platform_status reads
  through the gateway module's binding.
- test_gateway_prefix: COMPONENT_PREFIXES["gateway"] now includes
  "hermes_plugins" too.
- test_recommended_update_command_defaults_to_hermes_update: also
  short-circuit get_managed_update_command in case a stray
  ~/.hermes/.managed marker is present.
- test_user_id_is_not_explicit: _parse_target_ref now returns
  is_explicit=False for Slack U.../W... IDs (chat.postMessage rejects
  them — a DM must be opened first via conversations.open).

tools/send_message_tool.py

@@ -359,7 +359,14 @@ def _parse_target_ref(platform_name: str, target_ref: str):
             return match.group(1), match.group(2), True
         match = _SLACK_TARGET_RE.fullmatch(target_ref)
         if match:
-            return match.group(1), None, True
+            chat_id = match.group(1)
+            # Slack user IDs (U...) and workspace IDs (W...) are NOT valid
+            # explicit send targets — chat.postMessage rejects them. A DM
+            # must be opened first via conversations.open to get a D...
+            # conversation ID. Caller still gets the chat_id so the U→D
+            # resolution path in send_message() can run.
+            is_explicit = chat_id[0] not in {"U", "W"}
+            return chat_id, None, is_explicit
     if platform_name == "matrix":
         trimmed = target_ref.strip()
         split_idx = trimmed.rfind(":$")