fix(relay): reach cross-origin iframes; auto-reattach open (#35, #36)

#35: `open` auto-reattaches when the bound relay tab is gone — drops the dead
page, opens a fresh tab in the session's group, and navigates it, instead of
only `tab new` recovering.

#36: scroll and click now reach content inside cross-origin OOPIFs:
- scroll dispatches a real wheel at a viewport point (default center, --at x,y,
  or --frame n) so it scrolls the iframe under the pointer, which
  window.scrollBy on the top document silently no-ops on.
- over the extension relay, clicks always use DOM-dispatch instead of
  coordinate Input events — a coordinate event isn't confined to the target tab
  on a busy real Chrome (it drifted onto the foreground tab) and an OOPIF
  element's box can't be mapped to a top-viewport point.

skill-data/core/SKILL.md

@@ -287,6 +287,10 @@ chrome-use upload @e5 file1.pdf        # upload file(s) — works over the exten
                                           # a File there (chunked under native-messaging's 1 MiB cap).
                                           # Works on file <input>s and drop/paste composers (e.g. X).
 chrome-use scroll down 500             # scroll page (up/down/left/right)
+chrome-use scroll down 700 --at 640,400 # wheel at a pixel — scrolls a cross-origin
+                                          # iframe (Payments/Stripe/checkout/KYC) that
+                                          # plain page scroll can't reach
+chrome-use scroll down 700 --frame 2    # scroll frame 2 from `chrome-use frames`
 chrome-use scrollintoview @e1          # scroll element into view
 chrome-use drag @e1 @e2                # drag and drop
 ```