fix(slack): isolate doctor contract API (#63192)

* Slack: isolate doctor contract API

* chore: changelog

* fix(slack): move doctor changelog entry to Unreleased

* Plugins: lock Slack doctor sidecar metadata

* Slack: fix changelog entry placement

---------

Co-authored-by: @zimeg <zim@o526.net>
Co-authored-by: George Pickett <gpickett00@gmail.com>

src/plugins/bundled-plugin-metadata.test.ts

@@ -157,6 +157,13 @@ describe("bundled plugin metadata", () => {
     );
   });
 
+  it("keeps Slack's doctor contract sidecar on the bundled public surface", () => {
+    const slack = listRepoBundledPluginMetadata().find((entry) => entry.dirName === "slack");
+    expectArtifactPresence(slack?.publicSurfaceArtifacts, {
+      contains: ["doctor-contract-api.js"],
+    });
+  });
+
   it("loads tlon channel config metadata from the lightweight schema surface", () => {
     expect(collectRepoBundledChannelConfigsForTest("tlon")?.tlon).toEqual(
       expect.objectContaining({

src/plugins/doctor-contract-registry.test.ts

@@ -61,6 +61,30 @@ describe("doctor-contract-registry getJiti", () => {
     );
   });
 
+  it("prefers doctor-contract-api over the broader contract-api surface", () => {
+    const pluginRoot = makeTempDir();
+    fs.writeFileSync(
+      path.join(pluginRoot, "doctor-contract-api.js"),
+      "export default {};\n",
+      "utf-8",
+    );
+    fs.writeFileSync(path.join(pluginRoot, "contract-api.js"), "export default {};\n", "utf-8");
+    mocks.loadPluginManifestRegistry.mockReturnValue({
+      plugins: [{ id: "test-plugin", rootDir: pluginRoot }],
+      diagnostics: [],
+    });
+
+    listPluginDoctorLegacyConfigRules({
+      workspaceDir: pluginRoot,
+      env: {},
+    });
+
+    expect(mocks.createJiti).toHaveBeenCalledTimes(1);
+    expect(mocks.createJiti.mock.calls[0]?.[0]).toBe(
+      path.join(pluginRoot, "doctor-contract-api.js"),
+    );
+  });
+
   it("narrows touched-path doctor ids for scoped dry-run validation", () => {
     expect(
       collectRelevantDoctorPluginIdsForTouchedPaths({