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)

alembic/versions/0122_agent_definition_phase_f_fields.py

@@ -0,0 +1,66 @@
+"""Add Phase F fields to automation_agent_definitions.
+
+Adds temperature, max_tokens, max_steps, trace_mode, skill_ids,
+trigger_config, and ai_use_case_metadata to support the Phase F
+context-builder, SSE streaming, and AI-use-case features.
+
+Revision ID: 0122
+Revises: 0121
+"""
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import JSONB
+
+revision = "0122"
+down_revision = "0121"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column("temperature", sa.Float, nullable=False, server_default="0.3"),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column("max_tokens", sa.Integer, nullable=False, server_default="1000"),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column("max_steps", sa.Integer, nullable=False, server_default="20"),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column(
+            "trace_mode", sa.String(20), nullable=False, server_default="standard"
+        ),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column("skill_ids", JSONB, nullable=False, server_default=sa.text("'[]'::jsonb")),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column("trigger_config", JSONB, nullable=False, server_default=sa.text("'{}'::jsonb")),
+    )
+    op.add_column(
+        "automation_agent_definitions",
+        sa.Column(
+            "ai_use_case_metadata",
+            JSONB,
+            nullable=False,
+            server_default=sa.text("'{}'::jsonb"),
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("automation_agent_definitions", "ai_use_case_metadata")
+    op.drop_column("automation_agent_definitions", "trigger_config")
+    op.drop_column("automation_agent_definitions", "skill_ids")
+    op.drop_column("automation_agent_definitions", "trace_mode")
+    op.drop_column("automation_agent_definitions", "max_steps")
+    op.drop_column("automation_agent_definitions", "max_tokens")
+    op.drop_column("automation_agent_definitions", "temperature")