* feat(ui): version badge in status row + /feedback opens issue with diagnostic clipboard

When a user hits a bug, the first question back is "what version" — and
the only way to find out today is to drop to the shell. Filing the
issue itself means leaving the TUI, finding the repo URL, then either
remembering or re-collecting version / OS / terminal / Node / locale /
model. Both papercuts are easy to fix from the prompt-input surface.

- StatusRow shows a `v<VERSION>` pill on the right cluster, gated to
  cols ≥ 70 so it doesn't crowd narrow terminals.
- New `/feedback` slash: gathers version + platform + os release +
  TERM_PROGRAM/TERM + Node + locale + model + sessionId, writes a
  paste-ready Markdown block to the clipboard via the existing
  `writeClipboard` helper, then opens the GitHub new-issue URL in the
  default browser via a new cross-platform `openUrl` (win32 cmd /c
  start, darwin open, linux xdg-open). No-ops under CI / when
  REASONIX_NO_OPEN is set.
- Diagnostic body contains exactly the seven advertised fields and
  nothing else — `tests/feedback.test.ts` pins the field set and asserts
  no API keys / file paths / transcript content can leak through.

Closes esengine#499

* feat(ui): pre-fill /feedback issue body via URL + surface chip in status row

Two follow-ups so the affordance actually gets discovered and used:

- The issue page now opens with the diagnostic block already in the
  textarea via `?body=<urlencoded>`. Most users won't notice we copied
  to clipboard; pre-filling the URL is the obvious path. Clipboard
  stays as belt-and-suspenders for when the URL fails to open.
- StatusRow shows a `⚑ /feedback` hint after the version pill at
  cols ≥ 100 so users see the command exists. Narrower terminals (70–99
  cols) still get the version, just without the hint.
- Body length is capped at 6000 chars before encoding so a runaway
  diagnostic can't blow past the URL limit.

* feat(ui): expand /feedback diagnostic with flicker-relevant fields

The original block had version + platform + TERM_PROGRAM + Node + locale
+ model + session — fine for "agent ran the wrong tool" reports, but
useless for the rendering / flicker reports we actually field. Adds the
fields that come up first when triaging those:

- terminal size (cols×rows) — lots of repaint bugs only repro at
  specific widths
- env markers that change the rendering pipeline: COLORTERM,
  WT_SESSION, TMUX, SSH_TTY, WSL_DISTRO_NAME — TERM_PROGRAM alone can't
  distinguish cmd / WSL / SSH-tunnelled terminals
- theme name — different themes use different background fills, flicker
  is often theme-dependent
- edit / plan mode — decides which surfaces are mounted, changes
  repaint cadence
- latest version compare — surfaces "you're on an old build" without a
  follow-up question
- reasoning effort + MCP server count — incidentally cheap, occasionally
  load-bearing for cost / latency reports

Still no transcripts, paths, workspace name, or env outside the
hand-picked safe list. New tests pin the exact field set so future
fields can't sneak in unannounced.