iOS: no way to dismiss the keyboard — UNSUPPORTED_OPERATION leads to QuickType-bar mis-taps

[thymikee]

keyboard dismiss on iOS returns:

Error (UNSUPPORTED_OPERATION): Unable to dismiss the iOS keyboard without a native dismiss gesture or control

Benchmarked cost (AppControlBench, haiku_low element-08): after the failed dismiss the agent pressed a stale ref that now sat under the QuickType bar, appending a predictive suggestion — the sent message became "good morning TV" instead of "good morning" (same corruption signature as "Book TV" in haiku_high element-04). The keyboard being undismissable turns every post-typing interaction into a coordinate hazard.

Candidate approaches for the gap (to be validated live, in rough preference order):

1. iPad / keyboards with a dismiss key: tap the keyboard's own dismiss/hide affordance when the AX tree exposes one.
2. Focused-element resignation: end editing via the focused element (private AX action on the first responder, or the synthesized text-entry channel sending an end-editing event) — most faithful to "dismiss" semantics and AX-independent, consistent with the fix(ios): harden Bluesky-class interaction reliability #1588 synthesis direction.
3. Simulator hardware-keyboard toggle (Cmd+K equivalent) — hides the software keyboard on simulators; check whether it resigns focus or just hides chrome.
4. Safe-area tap fallback: tap a point chosen from the current snapshot that hits no interactive element (many apps resign focus on background tap) — app-dependent, last resort, must be disclosed in the response.

Whatever lands should also make keyboard dismiss's failure hint actionable (e.g. suggest press on a non-editable element or submit via type "\n" where appropriate) so agents stop tapping through the QuickType bar.