feat(F): F-CTX context_builder, F-STR agent_stream, F-DEF agent definition fields, F-SKILL skill_registry, F-TOOL agent_tools

- F-CTX: app/ai/context_builder.py (282 lines) — build_agent_context() + ReActSystemPromptBuilder
- F-STR: app/ai/agent_stream.py (155 lines) — stream_react_loop() with SSE events (step, status, done, error)
- F-DEF: AgentDefinition fields added (temperature, max_tokens, max_steps, trace_mode, skill_ids, trigger_config, ai_use_case_metadata) + migration 0122
- F-SKILL: app/ai/skill_registry.py (82 lines) — SkillDefinition + SkillRegistry singleton
- F-TOOL: app/ai/agent_tools.py (117 lines) — get_agent_tools() with permission intersection
- Skill CRUD routes: app/plugins/builtins/automation/skill_routes.py
- Tests: test_skill_registry.py (97 lines), test_agent_tools.py (219 lines)
- All Python compile checks pass, tests require PostgreSQL (infra issue, not code bug)

app/plugins/builtins/automation/agent_routes.py

@@ -59,6 +59,13 @@ def _agent_to_response(a: AgentDefinition) -> AgentDefinitionResponse:
         max_executions_per_hour=a.max_executions_per_hour,
         max_duration_seconds=a.max_duration_seconds,
         budget_limit_usd=a.budget_limit_usd,
+        temperature=a.temperature,
+        max_tokens=a.max_tokens,
+        max_steps=a.max_steps,
+        trace_mode=a.trace_mode,
+        skill_ids=[str(s) for s in (a.skill_ids or [])],
+        trigger_config=a.trigger_config or {},
+        ai_use_case_metadata=a.ai_use_case_metadata or {},
         created_by=str(a.created_by) if a.created_by else None,
         created_at=a.created_at.isoformat() if a.created_at else None,
         updated_at=a.updated_at.isoformat() if a.updated_at else None,