fix(spec): resolve circular import between spec.pipeline and core.client (ACS-302) (#1192)

* fix(spec): resolve circular import between spec.pipeline and core.client

Implement lazy imports via __getattr__ to break the circular import
chain where spec.pipeline.agent_runner imports core.client, which
imports agents.tools_pkg, which imports from spec.validate_pkg.

The import chain creates a cycle when spec/__init__.py imports
SpecOrchestrator at module level. By deferring these imports via
__getattr__, the import chain only executes when these symbols are
actually accessed, breaking the cycle.

This follows the established pattern used in core/__init__.py,
agents/__init__.py, and integrations/graphiti/__init__.py.

Refs: ACS-302

* refactor(spec): cache lazy imports in globals() for efficiency

Update __getattr__ to cache imported objects in globals() after
first access. This ensures subsequent accesses bypass __getattr__
entirely, avoiding redundant import overhead.

Also add return type annotation (-> Any) for Python 3.12+ compatibility.

Suggested-by: gemini-code-assist
Refs: ACS-302

---------

Co-authored-by: StillKnotKnown <stillknotknown@users.noreply.github.com>

apps/backend/spec/__init__.py

@@ -23,8 +23,17 @@ Usage:
     )
 
     success = await orchestrator.run()
+
+Note:
+    SpecOrchestrator and get_specs_dir are lazy-imported to avoid circular
+    dependencies between spec.pipeline and core.client. The import chain:
+    spec.pipeline.agent_runner imports core.client, which imports
+    agents.tools_pkg, which imports from spec.validate_pkg, causing a cycle
+    when spec/__init__.py imports SpecOrchestrator at module level.
 """
 
+from typing import Any
+
 from .complexity import (
     Complexity,
     ComplexityAnalyzer,
@@ -33,7 +42,6 @@ from .complexity import (
     save_assessment,
 )
 from .phases import PhaseExecutor, PhaseResult
-from .pipeline import SpecOrchestrator, get_specs_dir
 
 __all__ = [
     # Main orchestrator
@@ -49,3 +57,25 @@ __all__ = [
     "PhaseExecutor",
     "PhaseResult",
 ]
+
+
+def __getattr__(name: str) -> Any:
+    """Lazy imports to avoid circular dependencies with core.client.
+
+    The spec.pipeline module imports from core.client (via agent_runner.py),
+    which imports from agents.tools_pkg, which imports from spec.validate_pkg.
+    This creates a circular dependency when spec/__init__.py imports
+    SpecOrchestrator at module level.
+
+    By deferring these imports via __getattr__, the import chain only
+    executes when these symbols are actually accessed, breaking the cycle.
+
+    Imported objects are cached in globals() to avoid repeated imports.
+    """
+    if name in ("SpecOrchestrator", "get_specs_dir"):
+        from .pipeline import SpecOrchestrator, get_specs_dir
+
+        # Cache in globals so subsequent accesses bypass __getattr__
+        globals().update(SpecOrchestrator=SpecOrchestrator, get_specs_dir=get_specs_dir)
+        return globals()[name]
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")