chore: consolidate remaining tests into __tests__/ dirs and refactor mocks

Mostly mechanical cleanup left over from the earlier test-consolidation pass:
- Update import paths to ../../ for mocks now that test files moved deeper
- Simplify mock setup (drop usePluginUiSlots inline mock, etc.)
- Move engine ipc + runtimes tests into __tests__/ subdirs
- Move dashboard utils tests into __tests__/ subdir
- Refresh fusion-plugin-hermes-runtime/dist artifacts

build-exe.test.ts: spawn-import fix from a parallel branch (resolved during
worktree merge of the CSS extraction work).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/dashboard/app/utils/__tests__/highlightDiff.test.ts

@@ -0,0 +1,144 @@
+import { describe, it, expect } from "vitest";
+import { highlightDiff } from "../highlightDiff";
+import React from "react";
+
+type ElProps = { className?: string; children?: React.ReactNode };
+const propsOf = (el: React.ReactNode): ElProps =>
+  (el as React.ReactElement<ElProps>).props as ElProps;
+const typeOf = (el: React.ReactNode) =>
+  (el as React.ReactElement).type;
+
+describe("highlightDiff", () => {
+  it("applies diff-add class to added lines starting with +", () => {
+    const result = highlightDiff("+hello world");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe("span");
+    expect(propsOf(result[0]).className).toBe("diff-add");
+    expect(propsOf(result[0]).children).toBe("+hello world\n");
+  });
+
+  it("applies diff-del class to removed lines starting with -", () => {
+    const result = highlightDiff("-world");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe("span");
+    expect(propsOf(result[0]).className).toBe("diff-del");
+    expect(propsOf(result[0]).children).toBe("-world\n");
+  });
+
+  it("applies diff-hunk class to hunk headers starting with @@", () => {
+    const result = highlightDiff("@@ -1,5 +1,6 @@ function");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe("span");
+    expect(propsOf(result[0]).className).toBe("diff-hunk");
+    expect(propsOf(result[0]).children).toBe("@@ -1,5 +1,6 @@ function\n");
+  });
+
+  it("does not apply special class to context lines", () => {
+    const result = highlightDiff("  context line");
+    expect(result).toHaveLength(1);
+
+    // Context lines should be returned as plain text fragments
+    expect(typeOf(result[0])).toBe(React.Fragment);
+    expect(propsOf(result[0]).children).toBe("  context line\n");
+  });
+
+  it("does not apply diff-add class to +++ lines", () => {
+    const result = highlightDiff("+++ b/file.ts");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe(React.Fragment);
+    expect(propsOf(result[0]).children).toBe("+++ b/file.ts\n");
+  });
+
+  it("does not apply diff-del class to --- lines", () => {
+    const result = highlightDiff("--- a/file.ts");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe(React.Fragment);
+    expect(propsOf(result[0]).children).toBe("--- a/file.ts\n");
+  });
+
+  it("renders multiple lines correctly with different classes", () => {
+    const diff = `diff --git a/file.ts b/file.ts
+--- a/file.ts
++++ b/file.ts
+@@ -1,3 +1,4 @@
+ context line
++added line
+-deleted line
+  another context`;
+
+    const result = highlightDiff(diff);
+
+    expect(result).toHaveLength(8);
+
+    // Line 0: diff --git - plain fragment
+    expect(typeOf(result[0])).toBe(React.Fragment);
+
+    // Line 1: --- a/file.ts - plain fragment (not diff-del)
+    expect(typeOf(result[1])).toBe(React.Fragment);
+
+    // Line 2: +++ b/file.ts - plain fragment (not diff-add)
+    expect(typeOf(result[2])).toBe(React.Fragment);
+
+    // Line 3: @@ hunk header - diff-hunk
+    expect(typeOf(result[3])).toBe("span");
+    expect(propsOf(result[3]).className).toBe("diff-hunk");
+
+    // Line 4: context - plain fragment
+    expect(typeOf(result[4])).toBe(React.Fragment);
+
+    // Line 5: +added - diff-add
+    expect(typeOf(result[5])).toBe("span");
+    expect(propsOf(result[5]).className).toBe("diff-add");
+
+    // Line 6: -deleted - diff-del
+    expect(typeOf(result[6])).toBe("span");
+    expect(propsOf(result[6]).className).toBe("diff-del");
+
+    // Line 7: another context - plain fragment
+    expect(typeOf(result[7])).toBe(React.Fragment);
+  });
+
+  it("renders empty diff without errors", () => {
+    const result = highlightDiff("");
+    expect(result).toHaveLength(1);
+
+    // Empty string becomes single element with empty line
+    expect(typeOf(result[0])).toBe(React.Fragment);
+    expect(propsOf(result[0]).children).toBe("\n");
+  });
+
+  it("handles single line without newline", () => {
+    const result = highlightDiff("+single line");
+    expect(result).toHaveLength(1);
+
+    expect(typeOf(result[0])).toBe("span");
+    expect(propsOf(result[0]).className).toBe("diff-add");
+    expect(propsOf(result[0]).children).toBe("+single line\n");
+  });
+
+  it("handles diff header lines correctly", () => {
+    const diff = `diff --git a/src/index.ts b/src/index.ts
+index 1234567..abcdefg 100644
+--- a/src/index.ts
++++ b/src/index.ts
+@@ -10,6 +10,7 @@ export`;
+
+    const result = highlightDiff(diff);
+
+    // 5 lines total (split by \n)
+    expect(result).toHaveLength(5);
+
+    // All header lines should be plain fragments, not diff-add/diff-del
+    expect(typeOf(result[0])).toBe(React.Fragment);
+    expect(typeOf(result[1])).toBe(React.Fragment);
+    expect(typeOf(result[2])).toBe(React.Fragment); // --- a/src/index.ts
+    expect(typeOf(result[3])).toBe(React.Fragment); // +++ b/src/index.ts
+    expect(typeOf(result[4])).toBe("span");
+    expect(propsOf(result[4]).className).toBe("diff-hunk");
+  });
+});