refactor(tui): tighten editor handoff helpers

- editor.ts: collapse two private helpers into one flatMap-driven lookup,
  keep `isExecutable` as the only named primitive, document the fallback
  chain with prompt_toolkit parity
- editor.test.ts: hoist the `exe` helper out of `describe`, drop the
  empty afterEach + dead mkdir branch, materialize expected paths before
  the resolveEditor call so argument evaluation order doesn't bite
- useComposerState.openEditor: rmSync the mkdtemp dir (was leaking),
  early-return on bad exit / empty buffer, run cleanup in finally
- useInputHandlers: cheap `ch.toLowerCase() === 'g'` guard before the
  modifier check
- hermes-ink/screen.ts: pick up `npm run fix` import-sort cleanup so
  lint passes

ui-tui/src/lib/editor.ts

@@ -2,44 +2,13 @@ import { accessSync, constants } from 'node:fs'
 import { delimiter, join } from 'node:path'
 
 /**
- * Resolve which editor to launch when the user hits Ctrl+G / Alt+G.
- *
- * Order of preference:
- *   1. $VISUAL / $EDITOR (user's explicit choice)
- *   2. prompt_toolkit-compatible system fallback:
- *      editor → nano → pico → vi → emacs
- *   3. literal `'vi'` so spawnSync still has something to try
- *
- * This intentionally mirrors prompt_toolkit's Buffer.open_in_editor() picker
- * used by the classic CLI. In Cursor/VSCode terminals, nano is a better prompt
- * editing default than dropping casual users into vi's modal interface.
+ * Editor fallback chain when neither $VISUAL nor $EDITOR is set. Mirrors
+ * prompt_toolkit's `Buffer.open_in_editor()` picker so the classic CLI and
+ * the TUI launch the same editor on a given box.
  */
-export function resolveEditor(env: NodeJS.ProcessEnv = process.env): string {
-  return (
-    env.VISUAL ||
-    env.EDITOR ||
-    findEditor(env.PATH ?? '', 'editor', 'nano', 'pico', 'vi', 'emacs') ||
-    'vi'
-  )
-}
+const FALLBACKS = ['editor', 'nano', 'pico', 'vi', 'emacs']
 
-function findEditor(path: string, ...names: string[]): null | string {
-  const dirs = path.split(delimiter).filter(Boolean)
-
-  for (const name of names) {
-    for (const dir of dirs) {
-      const candidate = join(dir, name)
-
-      if (isExecutable(candidate)) {
-        return candidate
-      }
-    }
-  }
-
-  return null
-}
-
-function isExecutable(path: string): boolean {
+const isExecutable = (path: string): boolean => {
   try {
     accessSync(path, constants.X_OK)
 
@@ -48,3 +17,24 @@ function isExecutable(path: string): boolean {
     return false
   }
 }
+
+/**
+ * Resolve the editor to launch when the user hits Ctrl+G / Alt+G.
+ *
+ *   1. $VISUAL / $EDITOR (user's explicit choice)
+ *   2. first FALLBACKS entry resolvable on $PATH
+ *   3. literal `'vi'` so spawnSync still has something to try
+ */
+export const resolveEditor = (env: NodeJS.ProcessEnv = process.env): string => {
+  if (env.VISUAL) {
+    return env.VISUAL
+  }
+
+  if (env.EDITOR) {
+    return env.EDITOR
+  }
+
+  const dirs = (env.PATH ?? '').split(delimiter).filter(Boolean)
+
+  return FALLBACKS.flatMap(name => dirs.map(d => join(d, name))).find(isExecutable) ?? 'vi'
+}