fix(agent): full-catalog dashboard search and working LLM retry

- search_dashboards: call /api/dashboards with page_context=other and
  page_size=100 so the profile 'My Dashboards Only' filter can no longer
  hide the whole catalog; parse available_total/effective_profile_filter
  and report hidden-by-filter instead of a false 'no dashboards' answer
- prefetch_dashboards: same full-catalog context; fix dead code where
  data=resp.json() sat after return '' inside the error branch, making
  every 200 response raise NameError and the prefetch always return ''
- llm-status: ?force=1 bypasses the 30s health cache so the 'Retry now'
  button performs a fresh probe instead of re-reading the stale status;
  frontend keeps a single retry interval (previously stacked intervals
  decayed the countdown faster than 1/s and fired duplicate probes)
- tests: agent tool/prefetch, backend route bypass + force param,
  frontend retry/force coverage

shared/src/ss_tools/shared/_llm_health.py

@@ -42,10 +42,13 @@ _LLM_LAST_ERROR_TS_KEY = "last_llm_error_ts"
 
 
 # #region AgentChat.LlmHealth.Check [C:2] [TYPE Function] [SEMANTICS agent-chat,llm,health,check]
-async def _check_llm_provider_health() -> str:
-    """Check LLM provider connectivity. Cached for _LLM_CHECK_CACHE_TTL seconds."""
+async def _check_llm_provider_health(force: bool = False) -> str:
+    """Check LLM provider connectivity. Cached for _LLM_CHECK_CACHE_TTL seconds
+    unless force=True bypasses the cache for an immediate probe (used by the
+    frontend "Retry now" button — without force a click inside the TTL window
+    returned the stale cached status and appeared to do nothing)."""
     now = time.time()
-    if now - _llm_status["last_check_ts"] < _LLM_CHECK_CACHE_TTL:
+    if not force and now - _llm_status["last_check_ts"] < _LLM_CHECK_CACHE_TTL:
         return _llm_status["status"]
 
     # Fetch LLM config from backend's own API (same as agent container does)