chore(aria): derive yaml aria snapshots from the JSON snapshot

[Pavel Feldman (pavelfeldman)]

Make the JSON renderer the single source of the aria snapshot: type AriaNodeJSON explicitly, move yaml serialization (including codegen regex heuristics) into an isomorphic JSON=>yaml renderer, and serialize at the last moment before the yaml version is needed. Delete the duplicate yaml tree renderer and the text-based iframe snapshot merge.

[Yury Semikhatsky (yury-s)]

just do one case

[github-actions]

Test results for "tests 1"

4 flaky

⚠️ [chromium-library] › library/video.spec.ts:495 › screencast › should capture static page in persistent context Radoslav Kirilov (@smoke) `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/video.spec.ts:664 › screencast › should capture full viewport `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/video.spec.ts:699 › screencast › should capture full viewport on hidpi `@chromium-ubuntu-22.04-node20`

51353 passed, 1190 skipped

---

Merge workflow run.

[github-actions]

Test results for "MCP"

1 failed
❌ [firefox] › mcp/cli-core.spec.ts:198 › dialog-accept @mcp-windows-latest-firefox

8062 passed, 1284 skipped

---

Merge workflow run.

[github-actions]

Hi, I'm the Playwright bot and I took a first look at the CI failures here.

🟢 Clear — the one failure is a known pre-existing flake

mcp/cli-core.spec.ts:198 › dialog-accept on mcp-windows-latest-firefox is a Firefox/Windows dialog-timing flake, unrelated to this PR's aria-snapshot refactor. Everything else in the reports is flaky-only.

Details

This PR only reworks the aria snapshot renderer (packages/injected/src/ariaSnapshot.ts, packages/isomorphic/ariaSnapshotRenderer.ts, yaml.ts, JSON→yaml serialization). It doesn't touch MCP dialog handling or the click/dialog race.

Pre-existing flake / infra

• [firefox] › mcp/cli-core.spec.ts:198 › dialog-accept (@mcp-windows-latest-firefox) — pre-existing flake. Across the test-results DB it failed 16 of 1806 Firefox runs (~0.9%), every failure on mcp-windows-latest-firefox, spread over 16 distinct SHAs and unrelated PRs (fix(mcp): escape user input in codegen output #41962, feat(firefox): roll to r1539 #41970, chore(mcp): replace BackendManager with backend dispose callback and events #41982, test: roll stable-test-runner to 1.63.0-alpha-2026-07-27 #41999, feat(dialog): add dialogclosed event #42014, test: remove "page/page-evaluate.spec.ts:894 › promise collected" #42019, fix(cli): accept multiple files in upload command #42057, …). The test's own comment documents the cause: after the FF 153 roll, Firefox can deliver Page.dialogOpened after the default action timeout on Windows, so the click loses the modal race. Recent history for this bot:

  🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟥

• The "tests 1" report lists no failures — 4 flaky only (library/video.spec.ts screencast tests, library/beforeunload.spec.ts), all rescued on retry and none in code this PR touches.

Caused by this PR

• None found.

_{Triaged by the Playwright bot - agent run}