feat(routers): add API endpoints for agents and skills

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/app/routers/agent.py

@@ -6,6 +6,7 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.database import get_db
+from app.agents.learning.store import LearningArtifactStore, SessionRetrospectiveStore
 from app.agents.registry import load_builtin_registry_indexes
 from app.agents.runtime_metrics import coerce_cost_thresholds, estimate_token_cost, is_cost_budget_warning
 from app.models.agent import Agent
@@ -37,6 +38,7 @@ from app.schemas.agent import (
     AgentVisibilityVerifierOut,
 )
 from app.services.agent_service import _extract_continuity_snapshot
+from app.services.runtime_observability import build_runtime_observability_report
 
 router = APIRouter(prefix="/api/agents", tags=["Agent"])
 
@@ -662,6 +664,59 @@ async def get_visibility_tools(
     return _build_tool_governance(state, conversation_id=conversation_id)
 
 
+@router.get("/visibility/debug")
+async def get_visibility_debug(
+    conversation_id: str,
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    state = await _get_visibility_state(conversation_id, current_user=current_user, db=db)
+    observability = build_runtime_observability_report(
+        state=state,
+        feature_flags=dict(state.get("feature_flags") or {}),
+    )
+    retrospective_store = SessionRetrospectiveStore(db)
+    artifact_store = LearningArtifactStore(db)
+    recent_retrospectives = await retrospective_store.list_recent(
+        user_id=current_user.id,
+        limit=5,
+    )
+    recent_artifacts = await artifact_store.list_recent(
+        user_id=current_user.id,
+        limit=10,
+    )
+
+    return {
+        "conversation_id": conversation_id,
+        "observability": observability,
+        "skill_shortlist": list(state.get("skill_shortlist") or []),
+        "retrospective_shortlist": list(state.get("retrospective_shortlist") or []),
+        "merge_report": state.get("merge_report"),
+        "verification_report": state.get("verification_report"),
+        "recent_retrospectives": [
+            {
+                "id": item.id,
+                "task_type": item.task_type,
+                "summary": item.summary_text,
+                "execution_mode": item.execution_mode,
+                "verification_status": item.verification_status,
+                "recorded_at": item.recorded_at.isoformat() if item.recorded_at else None,
+            }
+            for item in recent_retrospectives
+        ],
+        "recent_learning_artifacts": [
+            {
+                "id": item.id,
+                "artifact_type": item.artifact_type,
+                "artifact_key": item.artifact_key,
+                "summary": item.summary_text,
+                "recorded_at": item.recorded_at.isoformat() if item.recorded_at else None,
+            }
+            for item in recent_artifacts
+        ],
+    }
+
+
 @router.post("", response_model=AgentOut, status_code=201)
 async def create_agent(
     data: AgentCreate,