fix: lazy-import anthropic SDK; tolerate LLM adapter failure in dry-run mode

--dry-run was crashing with ModuleNotFoundError because:
1. adapters/llm/anthropic.py imported 'anthropic' at module level
2. TeamRunner.__init__ always built the LLM adapter regardless of dry_run flag

Fixes:
- Move 'import anthropic' inside AnthropicAdapter.__init__ (lazy import)
  so the module loads cleanly without the SDK installed
- In TeamRunner.__init__, wrap _build_llm in a try/except when dry_run=True
  so missing adapter deps are logged as warnings, not fatal errors

dry-run now works with no third-party packages installed.

core/team_runner.py

@@ -177,7 +177,18 @@ class TeamRunner:
         adapter_cfg: dict = self._config.get("adapters", {})
         runtime_cfg: dict = self._config.get("runtime", {})
 
-        self._llm: LLMAdapter = self._build_llm(adapter_cfg.get("llm", "anthropic"))
+        if dry_run:
+            # In dry-run mode the LLM adapter is never actually called, so we
+            # tolerate missing dependencies (e.g. 'anthropic' SDK not installed).
+            try:
+                self._llm: LLMAdapter = self._build_llm(adapter_cfg.get("llm", "anthropic"))
+            except (ImportError, ValueError) as exc:
+                logger.warning(
+                    "LLM adapter unavailable in dry-run mode (%s) — continuing.", exc
+                )
+                self._llm = None  # type: ignore[assignment]
+        else:
+            self._llm = self._build_llm(adapter_cfg.get("llm", "anthropic"))
         self._vcs: Optional[VCSAdapter] = self._build_optional(  # type: ignore[assignment]
             _VCS_ADAPTERS, adapter_cfg.get("vcs"), "VCS"
         )