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/schemas.py

@@ -23,6 +23,13 @@ class AgentDefinitionCreate(BaseModel):
     max_executions_per_hour: int = Field(default=10, ge=1, le=1000)
     max_duration_seconds: int = Field(default=300, ge=1, le=86400)
     budget_limit_usd: float = Field(default=1.0, ge=0.0, le=10000.0)
+    temperature: float = Field(default=0.3, ge=0.0, le=2.0)
+    max_tokens: int = Field(default=1000, ge=1, le=100000)
+    max_steps: int = Field(default=20, ge=1, le=100)
+    trace_mode: str = Field(default="standard", pattern="^(standard|extended)$")
+    skill_ids: list[str] = Field(default_factory=list)
+    trigger_config: dict[str, Any] = Field(default_factory=dict)
+    ai_use_case_metadata: dict[str, Any] = Field(default_factory=dict)
 
 
 class AgentDefinitionUpdate(BaseModel):
@@ -326,3 +333,52 @@ class SubtaskListResponse(BaseModel):
 
     items: list[SubtaskRead]
     total: int
+
+
+# ─── Skill Definition Schemas (Phase F-SKILL) ───
+
+
+class SkillDefinitionCreate(BaseModel):
+    """Create a new skill definition."""
+
+    name: str = Field(..., min_length=1, max_length=255)
+    description: str = Field(..., min_length=1)
+    instructions: str = Field(..., min_length=1)
+    allowed_tool_ids: list[str] = Field(default_factory=list)
+    context_policy: dict[str, Any] | None = None
+    category: str = Field(default="general", max_length=100)
+    is_active: bool = Field(default=True)
+
+
+class SkillDefinitionUpdate(BaseModel):
+    """Update an existing skill definition (partial)."""
+
+    name: str | None = Field(None, min_length=1, max_length=255)
+    description: str | None = Field(None, min_length=1)
+    instructions: str | None = Field(None, min_length=1)
+    allowed_tool_ids: list[str] | None = None
+    context_policy: dict[str, Any] | None = None
+    category: str | None = Field(None, max_length=100)
+    is_active: bool | None = None
+
+
+class SkillDefinitionResponse(BaseModel):
+    """Skill definition response."""
+
+    id: str
+    name: str
+    description: str
+    instructions: str
+    allowed_tool_ids: list[str] = []
+    context_policy: dict[str, Any] | None = None
+    category: str = "general"
+    is_active: bool = True
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class SkillDefinitionListResponse(BaseModel):
+    """Paginated skill definition list."""
+
+    items: list[SkillDefinitionResponse]
+    total: int