test(browser): judge the modal test by drawn lines and pin a merged pull request

[RanolP]

The browser modal test (pnpm run test:modal in packages/browser) failed on main in both modes for reasons in the test itself, not the editor. This fixes only packages/browser/test/modal.mjs.

Fixture mode

• expandElided failed with "Enter expanded nothing", although Enter did draw the elided run (418 -> 427 lines). The test was waiting for a host expand console call, which the fixture never makes.
• Fix: both modes now judge Enter by the line count growing, waiting up to 15s.

Ext mode

• The merged-row check failed with "no merged row with del, ins and shared text". The extension opens the newest commit's diffset, and on the still-open feat: support bundled dev mode in ssr vitejs/vite#21626 that commit had drifted to one file with no such row.
• Fix: the test now opens fix(optimize-deps): avoid "unsupported" warnings for browser:false mappings vitejs/vite#23590 instead. It is merged, so its commits no longer change. Its newest commit edits one file, rolldownDepPlugin.ts, with 3 merged rows and elided runs.
• WARN: o did not move the selection was not a bug. On an identifier, the first parent node can span exactly the same text, so one o paints the same ranges. The check now presses o up to three times; here the selection widened on the second press (exactRegex -> { exactRegex, prefixRegex }).

Verification (headless Chromium only)

• pnpm run test:modal exits 0.
• fixture: passed.
• ext: passed. The merged-row step selected shared text after the second o. expandElided went from 34 to 54 lines.
• expandMove still logs "no cross-file move on this page, skipped" in ext mode, as it did before; that step was a skip already.

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