test: realign CI with current runtime contracts

[spytensor]

What changed

• make CI layers report independently and separate deterministic E2E from the browser smoke
• remove live-provider probes, skip-on-auth integration tests, permanently skipped onboarding examples, and the synthetic execution-summary smoke fixture
• align remaining tests with lazy tool activation, the L1 default permission, one-time approvals, current CLI routing, and current reasoning visibility
• narrow desktop packaging triggers and correct contributor/release/testing documentation

Root cause

The test stack had accumulated operational provider probes, stale examples, synthetic UI events, old permission assumptions, and workflow coupling. Those checks no longer represented the production contracts, so unrelated jobs cascaded red or skipped while obsolete tests reported misleading results.

Validation

• pnpm typecheck
• pnpm build:all
• focused Vitest rerun: 4 files, 63 tests passed
• completion/kernel focused rerun: 2 files, 14 tests passed
• pnpm verify:prompt-contract
• pnpm verify:public-export
• git diff --check
• workflow YAML parse and web smoke script syntax check
• Web UI smoke completed and wrote reports/web-ui-smoke.json

The public checkout does not contain docs/atlas/staleness.py, so no atlas report was generated.