step 3 complete: pluggable agent framework

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

BACKEND_PLAN.md

@@ -112,8 +112,8 @@ adiuva-api/
   - `UserProfile`: `id: str`, `email: str`, `tier: BillingTier`
 - **Outcome:** All request/response models defined and validated.
 
-### Step 3 — Agent Registry + base classes
-- [ ] `app/core/agent_registry.py`:
+### Step 3 — Agent Registry + base classes ✅
+- [x] `app/core/agent_registry.py`:
   - `BaseAgent(ABC)`:
     - `user_id: str`, `shared_memory: dict`, `vector_store_context: list[str]`, `skills: list[str]`
     - Abstract `get_name() -> str`, `get_description() -> str`
@@ -127,7 +127,7 @@ adiuva-api/
     - `get(name) -> ChatAgent`
     - `list_agents() -> list[dict]` — returns `[{name, description}]` for orchestrator prompt
     - `async call_agent(name, query, context) -> str` — for inter-agent calls
-- [ ] Unit tests: register, get, list, call_agent with mock
+- [x] Unit tests: register, get, list, call_agent with mock
 - **Outcome:** Pluggable agent framework.
 
 ### Step 4 — Orchestrator