Each test in test/releases-page.test.ts stands alone: no test leaves the repository public or the fixture half-built for the next #4694

Done:

• [ ] The test that flips the forge repository to public restores it to private in a finally, so one failure cannot turn the following tests (button, swapping-off, home link) red.
• [ ] The fixture's users are made without the password hash (insert directly or reuse the helper other suites use), so beforeAll does no slow work on a loaded check machine.
• [ ] "a writer's POST with swapping off is told so and nothing swaps" asserts the flash and that no swap began (gate state unchanged), and passes 20 runs in a row: for i in $(seq 20); do bun test test/releases-page.test.ts || break; done.

Files: test/releases-page.test.ts only; change src/ only if a test proves the handler wrong, and say so. Replaces #4671 (the sentinel's flake on this file); the same file's other two flakes are #4663 and #4681 — if their pulls have landed, rebase on them.