test(example): validate the PoC against the ask and close the gaps

- Web: actually tried. open and full-page screenshot work; --crop-on is
  refused (CROP_TARGET_NOT_ACCEPTED / PENDING_PIXEL_IDENTITY_EVIDENCE).
  Transcript in evidence/web-excerpt.json, issue 20.
- One reproduction sequence for both platforms with a table of the
  platform-specific values, instead of two diverging command blocks;
  the Android dev-launcher step is now in it. Points at the runner
  branch as the single-script form.
- Five issues filed on callstack/agent-device (#2579-#2583) and linked
  from issues.md.
- No em dashes; three self-certifying phrases removed.

Author: JKobrynski