docs: correct the stale CI-coverage claims in the handoff prompts [skip-ci]

[RonenMars]

What was wrong

Three root-level handoff prompts each carried a block of this shape:

Already established, do not re-derive. In .github/workflows/ci.yml: the full suite (Test (Node 20/22/24)) runs on ubuntu-latest only. There is a windows-latest runner, but it runs only npm run test:smoke and is continue-on-error: true — informational, never a merge gate.

Every clause after the first is false, and has been for a while:

• continue-on-error was removed on 2026-08-01, so a red platform job fails the PR.
• Smoke (macos-latest) and Smoke (windows-latest) are required checks in ruleset 17561930 (9 contexts), so a red one blocks the merge outright.
• Since ci: run the whole suite on macOS and Windows instead of an eight-file allowlist #527 both legs run the whole suite via npm test, not an eight-file allowlist, on a per-OS Node pin (macOS 24, Windows 22 — the latter tracked in P2: Node 24 crashes six vitest workers on Windows, so the Windows CI leg cannot run the pinned Node #530).

PROMPT-windows-smoke-gate.md additionally claimed main has no branch protection, citing gh api .../branches/main/protection returning Branch not protected.
That endpoint returns 404 on repos protected by a ruleset rather than classic branch protection, so the probe proved nothing and the conclusion pointed the wrong way — toward believing main is pushable.

Why the framing mattered more than the facts

Any doc can go stale. What makes these three different is that they say "do not re-derive" — an explicit instruction to the next reader to trust the paragraph without checking it.
A stale fact inside that block does not merely sit there; it propagates into whatever the reader does next, and it is protected from exactly the check that would catch it.

That is the same failure mode that let #523 merge green, and the same one that put a false Windows-coverage claim into docs/ROADMAP.md.
Correcting the facts without touching the framing would have left the mechanism in place.

What changed

• The stale paragraph is struck through, not deleted, with a dated correction above it. The record of what was believed, and when, is worth keeping in a handoff document; silently rewriting history would make the next reader trust it more, not less.
• PROMPT-windows-smoke-gate.md gets a DONE banner. The task it asks for was completed on 2026-08-01, so the live risk is someone running a prompt that re-does finished work against facts that no longer hold.
• Its three "facts already established" bullets are annotated individually — one was half-right in a way that mattered, one was wrong in a dangerous direction, one is simply superseded by a different sample.
• Two follow-on sentences that still read "it cannot block a merge" are corrected, since leaving them would contradict the correction two lines above.
• Every correction points at docs/testing/cross-platform-ci.md, which is maintained, rather than restating facts that will drift again.

What was deliberately left alone

LANDING-integration-to-main.md and docs/landing/* also mention test:smoke and the smoke job, but in past tense about what PR #332 and PR #340 contained.
Those statements are accurate history and were not touched.

Verified state

Checked 2026-08-11 against origin/main at 68aa91b.

• gh api repos/RonenMars/threadbase-streamer/rulesets/17561930 → 9 required contexts, including Smoke (macos-latest) and Smoke (windows-latest).
• .github/workflows/ci.yml:219 → run: npm test; :191 → node-version: ${{ matrix.node }}; matrix is macos-latest/24 and windows-latest/22.
• No continue-on-error anywhere in the workflow.

Docs-only, so the title carries [skip-ci].