feat(rpiv-ask-user-question): add global note on the Submit tab

`n` on the Submit tab opens the shared multiline notes editor against the
notes side-band's Submit pseudo-index (notesByTab[questions.length]).
doneFor lifts the committed note into QuestionnaireResult.globalNote via
conditional spread (attach-on-cancel, like per-question notes), and the
envelope appends a `global note: ...` segment before the zero-segments
decline check, so a note-alone submit is an answered result and note-free
results stay byte-identical. The Submit footer advertises the `n`
affordance via new locale keys; docs, tool schema, CHANGELOG, guidance
architecture files, and the regenerated submit-tab capture ride along.

Implements #182.