[P3.6] Retire permanently-skipped suites and replace tautological assertions

[frankbria]

Filed by the SaaS launch review. Priority P3.6 — severity low, category test-trust.

Problem

The green CI badge is the launch gate, and several checks cannot fail. ~1,050 lines of skipped tests inflate the apparent suite size while covering nothing: test_websocket_integration.py (877 lines, removed v1 protocol), test_dashboard_access.py (skipped with the factually false reason 'serve command is stub in v2'), and test_blocker_expiration_minimal.py which imports no product code and re-runs SQL copied from a method that no longer exists. Spec-less mocks mean a renamed GitHubIntegration method ships green and breaks cf pr merge; the ws_url fixture builds a ?token= URL the server rejects; and assertions like exit_code in (0, 1), 'merged appears in output' and a tautological hash-uniqueness test cannot detect the regressions they name.

Evidence

• tests/ui/test_websocket_integration.py:35
• tests/integration/test_dashboard_access.py:18
• tests/blockers/test_blocker_expiration_minimal.py:80
• tests/cli/test_pr_commands.py:56
• tests/ui/conftest.py:265
• tests/cli/test_v2_cli_integration.py:208

Acceptance criteria

• test_websocket_integration.py, test_dashboard_access.py and test_blocker_expiration_minimal.py are rewritten against v2 or deleted; the collected-skip count drops accordingly and the change is explained in the PR
• GitHubIntegration and conductor/runtime mocks use autospec/spec; renaming a mocked method makes at least one test fail (demonstrated in the PR)
• ws_url uses a stream ticket; the dead auto-'slow'-marking logic is removed
• No remaining exit_code in (0, 1) or lone assert result is not None in tests/cli and tests/ui; test_merge_pr_already_merged asserts merge_pull_request was not called; the rate-limit test asserts a 429 or is deleted

Dependencies

• blocked by [P1.30] Fix CI gates that pass without verifying anything #948 (P1.30)
• blocked by [P3.1] Delete the dead v1 backend layers #968 (P3.1)

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