🤖 a11y: device checks after the phone 16 px text-field rule (terminal, unmeasured forms, iPhone) #5995

Follow-ups that #5992 (fix for #5972) could not check on its Linux test host. #5992 removed the viewport zoom lock and raised text fields to 16 px on touch phones (globals.css, coarse-pointer block). None of these blocks #5972.

1. Terminal on a phone: ghostty-web sets contenteditable="true" on the terminal element, so the 16 px rule applies to it too. Ghostty draws on a canvas with its own font size, so the effect is likely harmless, and it also stops iOS from zooming when the terminal gets focus. Check cell size and fit on a phone, and that the fit logic ignores the element's font size.
2. Unmeasured forms: the Secrets add form, the Runtimes forms, and the sidebar rename and search popovers were not measured. Check that 16 px text does not overflow fixed-height inputs or select elements there.
3. Real iPhone check: confirm in Safari, both as a page and as a standalone app, that focusing the composer and other fields does not zoom the page, and that pinch zoom works.
4. Arbitrary size classes: the rule keeps fields with .text-lg to .text-3xl and lowers every other field to 16 px, including an arbitrary class such as text-[18px]. None exists today. A lint rule or a code comment at the shared Input would catch a new one.

Owner: coordinator desk. Trigger: access to an iPhone, a report of zoom on focus, or a field that adds a larger arbitrary size.

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