chore: bump WebKit version to 26.6

[Yury Semikhatsky (yury-s)]

Summary

• Bump reported WebKit version to 26.6 (upstream is at 626.1)

[github-actions]

Test results for "tests 1"

6 flaky

⚠️ [chromium-library] › library/browsertype-connect.spec.ts:891 › run-server › socks proxy › should proxy localhost requests Radoslav Kirilov (@smoke) `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/video.spec.ts:495 › screencast › should capture static page in persistent context Radoslav Kirilov (@smoke) `@realtime-time-library-chromium-linux`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:257 › third party 'Partitioned;' cookies `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:470 › top level 'Partitioned;' cookie and same origin iframe `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/trace-viewer-scrub.spec.ts:177 › should drag scrubber to select action `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-page] › page/page-event-request.spec.ts:181 › should return response body when Cross-Origin-Opener-Policy is set `@firefox-ubuntu-22.04-node20`

51311 passed, 1246 skipped

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Merge workflow run.

[github-actions]

Test results for "MCP"

3 failed
❌ [chrome] › mcp/annotate.spec.ts:173 › user-initiated annotate downloads zip with feedback.md @mcp-windows-latest-chrome
❌ [chrome] › mcp/annotate.spec.ts:349 › should annotate when context has no fixed viewport @mcp-windows-latest-chrome
❌ [firefox] › mcp/cli-core.spec.ts:131 › check @mcp-windows-latest-firefox

8272 passed, 1371 skipped

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Merge workflow run.

[github-actions]

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

🟢 The PR is clear — all failures are pre-existing flakes

This PR only bumps the reported WebKit version (browsers.json, wkBrowser.ts, the README badge, and device-descriptor user-agent strings). The 3 CI failures are all Chrome/Firefox MCP tests on Windows, which don't exercise WebKit at all — and each one flips verdict across many unrelated runs in the test-results DB.

Details

The library shards are green (only 6 within-run flakes, all rescued on retry). The only real failures are in the MCP shard, and all three are confirmed pre-existing flakes:

Pre-existing flake / infra

• [chrome] › mcp/annotate.spec.ts:349 › should annotate when context has no fixed viewport — flaky across runs: 3 failed / 730 passed over 733 runs. Also failed on unrelated PRs feat(storage): capture OPFS in storage state #42248 (sha fccba478) and fix(mcp): refuse browser_close when the browser context is shared #42495 (sha 1b81ed67), plus flakes on msedge (3/718).
• [chrome] › mcp/annotate.spec.ts:173 › user-initiated annotate downloads zip with feedback.md — flaky across runs: 1 failed / 732 passed. Also failed on unrelated PR chore(deps-dev): bump browserslist from 4.28.4 to 4.28.8 #42489 (sha 80fb1e9b) and a push run (sha 66bfad76).
• [firefox] › mcp/cli-core.spec.ts:131 › check — flaky across runs: 5 failed / 716 passed. Also failed on unrelated PRs feat(locator): page-free by locators resolved with page.get() #42157, test(chromium): fixme flaky "should ignore page.pause when headed" on macOS #41959, fix(tracing): allow restarting tracing after a failed stop #42425, fix(video): embed recording start time in WebM metadata #42478 and a push run.

None of these code paths touch WebKit version reporting, so this diff can't be responsible for them.

_{Triaged by the Playwright bot - agent run}