feat(editor): own input via a hidden focusable textarea (ADR-036)

[myrddian]

First step of ADR-036 (recorded in #4 — merge that first for the ADR text, though this stands alone).

Problem

editor.ts listened on document for keydown. So does input.ts. Nothing coordinated the two — the only thing keeping them apart was the server having sent input.prompt {mode: "none"} for that screen (WizardFormApp.defaultInputPrompt). Any editor-bearing screen that forgot got every keystroke handled twice.

Downstream of the same choice: no IME support anywhere in the frontend, no paste path in the editor, nothing for assistive tech to focus, and no mobile on-screen keyboard — a keyboard needs a focused input, which is exactly why input.ts uses one (#42).

Change

Each editor owns a hidden-but-focusable <textarea> and reads keys from it. Focus becomes the arbiter, so the coordination problem goes away structurally rather than by convention. mode: "none" still gets sent; it's now an optimisation, not a correctness requirement.

Painting stays fully custom — the terminal aesthetic is untouched. Repaints replace a separate paintNode, never mountNode, so the key source survives every keystroke. Re-creating it 60×/minute would drop focus and make IME composition impossible.

This is the Ace / CodeMirror 5 / Monaco split: native input handling, custom painting.

Bug found by the tests

renderEditor runs while the subtree is still detached — the caller attaches it afterwards — so .focus() silently did nothing. Not a test artifact: main.ts has the same ordering, so the editor never took focus in the browser either. Fixed with an explicit focusActiveEditor() after the attaching replaceChildren, rather than a timing hack.

focusKeyInput() takes focus but never steals it: if another field has focus it stays there. Strictly less aggressive than swallowing every document keystroke.

Verification

• 5 new tests, 68 passing across 11 files
• tsc --noEmit clean, bundle builds
• The regression test that matters: a keydown on document.body no longer reaches the editor

Not verified: real mobile keyboard, IME, and paste. This is tests-in-happy-dom only. The textarea makes them possible; composition still needs explicit compositionstart/compositionend handling, which is deliberately not in this change.

Next

Reconciling paint instead of replaceChildren — retires the activeEditor singleton and the findEditorId pre-scan, and makes viewport.resize safe by construction rather than by a guard.