feat(FN-3976): reclassify github import action gating

Completes FN-3976 by reclassifying GitHub import action gating in the engine's `gating-classifications.ts`, updating documentation in `docs/agents.md` accordingly, and adding test coverage across four gating test suites.

Fusion-Task-Id: FN-3976

packages/engine/src/__tests__/gating-classifications-provisioning.test.ts

@@ -17,4 +17,13 @@ describe("gating classifications provisioning split", () => {
     expect(TASK_AGENT_MUTATION_TOOLS.has("fn_agent_create")).toBe(true);
     expect(TASK_AGENT_MUTATION_TOOLS.has("fn_agent_delete")).toBe(true);
   });
+
+  it("classifies github task imports as action-gated task mutations only", () => {
+    expect(ACTION_GATE_TASK_AGENT_MANAGEMENT_TOOLS.has("fn_task_import_github")).toBe(true);
+    expect(ACTION_GATE_TASK_AGENT_MANAGEMENT_TOOLS.has("fn_task_import_github_issue")).toBe(true);
+    expect(PERMANENT_AGENT_TASK_MUTATION_TOOLS.has("fn_task_import_github")).toBe(false);
+    expect(PERMANENT_AGENT_TASK_MUTATION_TOOLS.has("fn_task_import_github_issue")).toBe(false);
+    expect(TASK_AGENT_MUTATION_TOOLS.has("fn_task_import_github")).toBe(true);
+    expect(TASK_AGENT_MUTATION_TOOLS.has("fn_task_import_github_issue")).toBe(true);
+  });
 });