[codex] Deflake visitorId e2e assertion

[JuroUhlar]

Summary

• replace the fixed 5 second sleep in the visitorId Playwright test with a polling assertion
• wait until each <code> result block contains parseable JSON with a valid visitorId/requestId pair
• add runtime guards so partial or malformed intermediate content is treated as not-ready instead of failing immediately

Why

The e2e test was flaky because it read and parsed the result element once after a fixed delay. When the page had rendered the element but had not populated valid JSON yet, the test failed even though the result would appear shortly after.

[github-actions]

⚠️ This PR doesn't contain any changesets. If there are user-facing changes, don't forget to run:

pnpm exec changeset

to create a changeset.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟢	Statements	99.61%	256/257
🟢	Branches	99.08%	108/109
🟢	Functions	100%	55/55
🟢	Lines	99.6%	251/252

Test suite run success

273 tests passing in 94 suites.

Report generated by 🧪jest coverage report action from 9d9d383

Show full coverage report

St	File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
🟢	All files	99.61	99.08	100	99.6
🟢	src	100	100	100	100
🟢	config.ts	100	100	100	100
🟢	env.ts	100	100	100	100
🟢	handler.ts	100	100	100	100
🟢	index.ts	100	100	100	100
🟢	src/handlers	98.7	96.15	100	98.66
🟢	...ApiRequest.ts	96.42	87.5	100	96.15	79
🟢	...StatusPage.ts	100	100	100	100
🟢	src/utils	100	100	100	100
🟢	...ionHeaders.ts	100	100	100	100
🟢	...Monitoring.ts	100	100	100	100
🟢	cookie.ts	100	100	100	100
🟢	...orResponse.ts	100	100	100	100
🟢	...WithMaxAge.ts	100	100	100	100
🟢	...AgeIfLower.ts	100	100	100	100
🟢	proxyEndpoint.ts	100	100	100	100
🟢	...tpResponse.ts	100	100	100	100
🟢	routing.ts	100	100	100	100