tests/docs: cover diffs skill loading behavior

extensions/diffs/README.md

@@ -16,6 +16,8 @@ The tool can return:
 - `details.filePath`: a local rendered artifact path when file rendering is requested
 - `details.fileFormat`: the rendered file format (`png` or `pdf`)
 
+When the plugin is enabled, it also ships a companion skill from `skills/` that guides when to use `diffs`. This guidance is delivered through normal skill loading, not unconditional prompt-hook injection on every turn.
+
 This means an agent can:
 
 - call `diffs` with `mode=view`, then pass `details.viewerUrl` to `canvas present`

src/agents/skills.loadworkspaceskillentries.test.ts

@@ -139,4 +139,20 @@ describe("loadWorkspaceSkillEntries", () => {
 
     expect(entries.map((entry) => entry.skill.name)).toContain("diffs");
   });
+
+  it("excludes diffs plugin skill when the plugin is disabled", async () => {
+    const { workspaceDir, managedDir, bundledDir } = await setupWorkspaceWithDiffsPlugin();
+
+    const entries = loadWorkspaceSkillEntries(workspaceDir, {
+      config: {
+        plugins: {
+          entries: { diffs: { enabled: false } },
+        },
+      },
+      managedSkillsDir: managedDir,
+      bundledSkillsDir: bundledDir,
+    });
+
+    expect(entries.map((entry) => entry.skill.name)).not.toContain("diffs");
+  });
 });