fix(scripts): address Copilot review round 1 on #2147

- pty.mjs: narrow the BSD argv set to {darwin, freebsd}. Grouping every
  BSD together was wrong — NetBSD's `script` takes the command through
  `-c`, so the argv form fails at `script` startup, which this smoke would
  then report as a TUI crash. Rather than add an unverified `-c` branch
  for netbsd/openbsd, they fall through to `null` and the smoke skips with
  the reason: a guessed invocation turns a clean skip into a false failure
  while looking like support.

- pty.test.mjs: "supported unless Windows" would fail `test:scripts` on
  aix/sunos/netbsd/openbsd, where a null wrapper is correct and the smoke
  skips by design. State the policy once (SUPPORTED_PLATFORMS) and branch
  on it, keeping the real-probe teeth that catch a `script` missing from
  PATH. Pin netbsd/openbsd/aix/sunos to null in scriptFlavorFor's tests
  so "unsupported" reads as the default, not a win32 special case.

- render-smoke.mjs: the @returns contract claimed a close guarantee the
  code does not give — both drain give-up branches resolve after only a
  warning, so output can be truncated and the child may still hold the
  work dir. Document the bounded fallback and name the required cleanup
  shape (removeSafe, not rmSync), since a caller "tightening" cleanup on
  the old wording would reintroduce #1801 exactly where it doesn't hold.

- AGENTS.md, clients/launcher/README.md: drop the pre-#2111 claim that the
  smokes build test-servers "on demand if it is missing". ensureTestServers
  rebuilds unconditionally, once per process — presence is not freshness.

- .github/copilot-instructions.md: mirror the survival rule, per the
  same-PR mirroring requirement. One bullet, generalized past this fix:
  a smoke must assert the thing survives, not that it started, and the
  started-then-died branch belongs in a scripts/lib test against a stub.

Signed-off-by: Cliff Hall <cliff@futurescale.com>
Signed-off-by: cliffhall <cliff@futurescale.com>

clients/launcher/README.md

@@ -99,7 +99,9 @@ through the built launcher artifact (beyond the `--help` checks in
   local-only (self-skips under `CI`), which is precisely where a false green
   goes unnoticed.
 
-Both build `test-servers/build` on demand if it is missing.
+Both rebuild `test-servers/build` on **every run** — once per process, whether
+or not it already exists (#2111). Presence is not freshness: a smoke driving a
+stale fixture reports a product failure rather than a staleness one.
 
 ## Development