R-01/R-02/R-07/R-10/R-17: plain, reassuring in-app status legibility & a11y copy

[ChelseaKR]

Make evidence-status legible and reassuring in the app, and leave no screen a
dead end for a stressed user:

• EN/ES status copy (R-01, R-17): reword "Awaiting timestamp" -> "Waiting for a
  trusted timestamp" and add a visible reassurance paragraph (associated via
  aria-describedby) explaining the photo is already sealed on-device and that a
  wait, even a long one, does not weaken the evidence; a calm "nothing more to
  do" once everything is timestamped. Toggled by deferred count in renderStatus.
• No dead-end empty states (R-02): issues_empty_next (wired into #issues-empty)
  and a next-action issue_none_available so every idle state names what to do.
• ARIA live-region announcements (R-07): keep the existing clear-then-set
  announce(); capture/resolve/export each announce their outcome
  (awaiting->timestamped via msg_resolved).
• Non-auditory success cue (R-10): signalSuccess() adds navigator.vibrate(35)
  plus a prefers-reduced-motion-guarded .flash-ok pulse on the announcer, on
  capture, resolve, and verified export. The aria-live text stays primary.

Mark these done in-app in the persona execution log and backlog.

Static-shell only: no new dependencies, offline-first preserved. Validated with
make test (196 passed), including the real browser axe scan (EN+ES),
keyboard/structural a11y, and EN/ES i18n key-parity gates; both help-copy
branches observed live in EN and ES.

Co-Authored-By: Claude Fable 5 noreply@anthropic.com

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Backfill PR for a completed roadmap item (roadmap/status-legibility-and-a11y-copy-fixes-r-, 1 commit(s) over main). Part of the portfolio roadmap batch.