Address remaining review comments for peer dependency warnings

Test improvements:
- Line 7681: Use line-anchored regex pattern /^warn:[^\n]*...$/ to
  match only single lines (same fix as line 3916)

Regression test 26076 rewrite:
- Remove setDefaultTimeout and use local VerdaccioRegistry instead
  of network npm to make test hermetic and fast
- Fix await order: await stdout/stderr BEFORE exited for better
  error messages on failure
- Update regex pattern to support scoped packages and hyphenated
  names using /[@\w./-]+/ instead of /\w+/
- Publish test packages locally to create controlled peer dep
  mismatch scenario

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/cli/install/bun-install-registry.test.ts

@@ -7678,7 +7678,10 @@ describe("yarn tests", () => {
     expect(err).not.toContain("error:");
     expect(err).not.toContain("not found");
     // New improved peer dependency warning format shows the requiring package, expected version, and actual version
-    expect(err).toMatch(/warn:.*peer-deps-fixed has unmet peer dependency no-deps@\^1\.0\.0 \(found 2\.0\.0\)/);
+    // Use line-anchored pattern to avoid matching across lines
+    expect(err).toMatch(
+      /^warn:[^\n]*peer-deps-fixed[^\n]*has unmet peer dependency no-deps@\^1\.0\.0 \(found 2\.0\.0\)$/m,
+    );
     expect(out.replace(/\s*\[[0-9\.]+m?s\]\s*$/, "").split(/\r?\n/)).toEqual([
       expect.stringContaining("bun install v1."),
       "",