docs(wsl): record the two traps the real-WSL run surfaced

Both were found running the four `*.wsl.test.ts` suites against a live
Ubuntu-24.04 distro — the first time any of them had executed.

Lane ratchet header, next to the existing "does a registered suite EXECUTE"
prose, because that is where someone will look:

  - nothing in `.github/` or `config/` sets any `ORCA_REAL_WSL_*` variable, so
    all four suites ran on no machine until exported by hand. They pass; that
    was not knowable from a green board.
  - these gates are compared with `===`, and `set VAR=1 && cmd` in cmd.exe
    stores `"1 "`. Trailing space, gate shut, and the suite reports "skipped"
    exactly as it does when the variable was never set. I filed that as a repo
    defect for several minutes before checking my own shell. A gate whose closed
    state is indistinguishable from its unset state is a gate nobody is running.
  - registered, triggered, and unable to fail are three separate ways to be
    invisible. The banner suite was all three at once.

Runner suite header: it appends `sleep 60` to the shared distro user's
`~/.profile` and backs up to a fixed path with `|| true`, whose teardown
fallback is `rm -f "$HOME/.profile"`. The teardown works — it has no margin.
An aborted run leaves every new login stalling a minute, or deletes the profile.
The note says not to run it against a shared distro, and gives the check to
repeat if you must: hash `$HOME/.profile` either side, never assume the restore.

Comments only; no assertion or behaviour changes. Both lane ratchets stay green.

config/scripts/win32-test-lane-registration.test.mjs

@@ -59,9 +59,22 @@ import { classifyPrJobs } from './pr-code-change-scope.mjs'
  *   - whether a registered suite EXECUTES. Registration is what is asserted. A
  *     suite gated on win32 plus an env var stays skipped on the CI runner even
  *     when registered -- see MANUAL_OPT_IN -- and a path registered but gated
- *     for another platform is not caught either.
+ *     for another platform is not caught either. Measured 2026-09: nothing in
+ *     `.github/` or `config/` sets any `ORCA_REAL_WSL_*` variable, so all four
+ *     `*.wsl.test.ts` suites ran on no machine until someone exported them by
+ *     hand. They pass; that was not knowable from the board.
+ *   - that an env-var gate can be OPENED. These are compared with `===`, and
+ *     `set VAR=1 && cmd` in cmd.exe stores `"1 "` -- trailing space, gate shut,
+ *     suite reports "skipped" exactly as it does when you never set it. Prefer
+ *     `set "VAR=1"`, and prefer a gate whose closed state is distinguishable
+ *     from its unset state. A gate nobody can open is a gate nobody is running.
  *   - whether the `package_windows` job is triggered for a given diff, or
- *     whether the registered test asserts anything worth running.
+ *     whether the registered test asserts anything worth running. The second
+ *     half is not hypothetical: `local-worktree-filesystem-wsl-banner.wsl.test.ts`
+ *     was registered, opt-in, green -- and could not fail, because its contrast
+ *     row used `endsWith` and the banner it contrasts against is conditional on
+ *     distro user state. Registered, triggered and unable to fail are three
+ *     separate ways to be invisible.
  *
  * Growth of the two grandfathered lists is capped by literals, but only review
  * stops someone raising a cap. The caps make that an explicit, visible edit.

src/main/wsl/wsl-runner.wsl.test.ts

@@ -11,6 +11,18 @@ import { resolveWslExecutablePath } from './wsl-executable-path'
  * Gated behind an env var and win32 because it mutates the distro's `~/.profile`
  * to reproduce #14288. Run with:
  *   ORCA_REAL_WSL_RUNNER_TEST=1 pnpm vitest run src/main/wsl/wsl-runner.wsl.test.ts
+ *
+ * DO NOT run this against a distro you share. The teardown below works, but it
+ * has no margin, and all three of its failure modes land on a real user:
+ *   - the appended `sleep 60` is in `$HOME/.profile` for the duration, so any
+ *     login shell started in that window stalls a minute;
+ *   - an aborted run (crash, timeout, Ctrl-C) never reaches `afterAll`, and the
+ *     stall becomes permanent;
+ *   - the backup is `cp … || true` to a FIXED path, so if it fails, or a stale
+ *     copy from an earlier abort is present, teardown's `|| rm -f "$HOME/.profile"`
+ *     deletes or reverts the user's profile.
+ * Verified by hashing `$HOME/.profile` either side of a run, which is the check
+ * to repeat if you must run it somewhere shared -- do not assume the restore.
  */
 const DISTRO = process.env.ORCA_WSL_TEST_DISTRO ?? 'Ubuntu-24.04'
 const enabled = process.platform === 'win32' && process.env.ORCA_REAL_WSL_RUNNER_TEST === '1'