Refresh Web lifecycle acceptance selectors

[sam2tom]

Summary

• Refresh lifecycle acceptance selectors for the current Web copy and accessibility labels.
• Use the appearance menu for dark-theme checks and the current Sessions refresh control.
• Retain coverage for Session streaming, deletion, retries, Templates, and Environment status instead of removing working behavior tests.

Validation

• pnpm typecheck — passed
• pnpm test:web — 409 client and 781 Web tests passed
• pnpm test:core-doctor — 63 tests passed
• pnpm --filter @agents-core-web/web build — passed
• pnpm test:web:acceptance -- --reporter=line — 145/147 passed; the remaining two old Environment-label assertions were then corrected
• Focused Playwright rerun of those two cases — 2/2 passed
• git diff --check — passed
• make check — reached check-database after distribution checks; this machine has no dedicated PARSAR_AGENTS_API_TEST_DATABASE_URL

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