quoteCmdArg corrupts arguments containing a literal `"` on cmd surfaces

Iniziate da dor/src/commands/shell-quote.ts, in corrispondenza di quoteCmdArg, e rivedete le aspettative esistenti in dor/test/cli-output.test.mjs intorno alle righe 204-206. Convalidate il comportamento scelto per le virgolette letterali su un host Windows cmd.exe, quindi aggiungete un caso di regressione con virgolette incorporate e confermate che il programma avviato riceva l'argomento originale.

quoteCmdArg corrupts arguments containing a literal " on cmd surfaces

When dor forwards a command tail (dor split -- …, dor ensure …) to a pane whose shell is cmd.exe, the host renders the argv with quoteCmdArg. For any argument that contains a double-quote, the output is malformed.

Trace

function quoteCmdArg(arg: string): string {
  if (arg === '') return '""';
  const escaped = arg
    .replace(/[%]/g, '%%')
    .replace(/([&|<>()^"])/g, '^$1');   // caret-escapes the "
  if (WINDOWS_SAFE_ARG.test(arg)) return escaped;
  return `"${escaped}"`;                 // ...then wraps the result in quotes
}

For arg = 'say "hi"' the function:

1. caret-escapes each " → say ^"hi^", then
2. wraps in surrounding quotes → "say ^"hi^"".

Inside a cmd double-quoted region, ^ is not an escape character — it is literal. So the embedded ^" does not produce an escaped quote; the first ^" is read as a literal ^ followed by a quote that closes the surrounding quoted region early, and the rest of the argument is re-parsed outside quotes. The argument the launched program receives is not say "hi".

The same belt-and-suspenders pattern (caret-escape and wrap in quotes) is what the existing test pins for a&b → "a^&b" (cli-output.test.mjs:204-206); for &/(/) the caret inside quotes is merely redundant (those chars are already literal inside quotes), so it's harmless-but-odd. For " it is actively wrong, and that case is untested.

Why this needs maintainer input rather than a drive-by fix

Correct cmd-line quoting for a literal " depends on how the receiving program parses its command line (the msvcrt/CommandLineToArgvW convention uses \" and ""; a bare cmd builtin differs). Picking the right escaping is a design decision that should be validated on an actual Windows + cmd.exe host, which this CI environment can't do. Flagging rather than guessing.

Suggested direction (needs Windows verification)

For the cmd kind, escape an embedded " by doubling it ("") or backslash-escaping (\") inside the wrapped form, and don't caret-escape characters that already sit inside the surrounding quotes. Add a cli-output.test.mjs case with an embedded " to pin whatever behavior is chosen.

Surfaced by the nightly code-quality survey.