fix(ci): speed up tall-prompt Storybook setup

[liuxiaocs7]

Summary

Preparing the 80-line prompt fixture through thousands of synthetic keystrokes can consume Storybook's 15-second deadline before submission and scroll assertions run. Insert each line natively, keep Shift+Enter and submission on the real keyboard path, and assert the complete draft before checking scrolling.

• Remove four unreferenced module-page comparison PNGs.
• Normalize the ASF headers in the repository-only Codex executor example in a separate commit. /scripts/plugins is excluded from source archives through export-ignore.

Fixes #5490. Its transcript measure-ahead change already landed in #5499 (2,000 to 4,000 px), and the WorkHub navigation-highlight check was removed with the Work rail in #5622.

Verification

After rebasing onto c299cc17a:

• Workspace dependency build, lint, formatting, Storybook typecheck and Storybook build passed.
• Eight focused prompt-submission and WorkHub stories passed with four concurrent workers, the existing 15-second deadline, and no retries.
• git diff --check and the protocol epoch guard against main passed.
• The net diff matches the reviewed version, accounting for upstream line offsets; the license cleanup is now a separate commit.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Codex prepared the Storybook fix and cleanup, rebased the branch, updated the PR description, and ran validation.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[Astro-Han]

Reviewed at 4557a4ce0. The remaining code change is solid — execCommand('insertText') exercises the real beforeinput→Astryx→onChange→saveCurrentDraft path, Shift+Enter/submission stay on real keydown, and the assertions are stronger (full-draft innerText check). PNG removals are unreferenced. No code blockers.

P2 — the title/body no longer describe this diff. Two of the three claimed changes dissolved on rebase: the 2,000→4,000 measure-ahead margin already landed via #5499 (and #5499's justification is more complete — 6,000 triggers traversal-story per-step drift), and the WorkHub navigation-highlight wait was removed along with the Work rail in #5622. The squash title stabilize Storybook setup and transcript measurements would enter main history with no transcript-measurement change in it. Suggest retitling to the actual scope (tall-prompt insertion + PNG cleanup + plugin license headers) and noting on #5490 which parts landed where.

P3 inline — undeclared scope: ASF headers on scripts/plugins/codex-app-server-executor/*. Benign and self-consistent, but /scripts/plugins is export-ignore and the header check already passed without them — disclose in the body or split out.