[ZEPPELIN-6668] Add notebook route benchmark contract

[voidmatcha]

What is this PR for?

Add a reproducible benchmark contract for the notebook route, without committing baseline numbers (a follow-up records them).

• Fixture: 100 paragraphs (80 TEXT, 10 TABLE, 10 collapsed), pinned by SHA-256
• Ready condition: action bar visible, 100 paragraph containers, first Monaco editor attached
• Runs: 10 cold (new context) and 10 warm (after one unrecorded prime), with raw samples, median, and p95
• Bundles: raw and gzip sizes of the Angular entry chunks and React remoteEntry.js

Runtime metrics cover the Angular route only. The benchmark is excluded from the normal E2E run.

Most of the diff (3,319 of 3,957 added lines) is the fixture JSON. It is data, pinned by SHA-256 and checked for composition by validateFixture, so it does not need a line-by-line review. The code to review is about 590 lines under e2e/performance/, e2e/models/notebook-performance-page.ts, test/notebook-baseline.spec.ts and playwright.performance.config.js.

What type of PR is it?

Improvement

Todos

• Add a hash-pinned benchmark fixture
• Add the Playwright performance runner
• Validate the benchmark contract with unit tests

What is the Jira issue?

ZEPPELIN-6668

How should this be tested?

cd zeppelin-web-angular
npm run test:shell -- test/notebook-baseline.spec.ts
# against an isolated Zeppelin serving the `npm run build` output
PLAYWRIGHT_BASE_URL=http://localhost:8080 PERF_NOTEBOOK_DISPOSABLE=1 PERF_NOTEBOOK_DRY_RUN=1 npm run perf:notebook-baseline

A local dry run passes (1 cold + 1 warm, every summary field recorded). Use localhost: the server rejects a 127.0.0.1 WebSocket origin unless zeppelin.server.allowed.origins is set.

Screenshots (if appropriate)

N/A

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? Yes - e2e/performance/README.md