style(mobile): put every document import back in its import block

pullfrog caught `fit-scale`, where `scheduleDocumentFrame` sat below `MIN_FIT_COLS`. A
statement walk over all 41 non-test modules under `document/` — the tree, not a grep, so a
multi-line import or one inside a comment cannot hide — found one more: `host-notify` split
its two `document-host-seams` lines around the re-export between them. Both imports moved up;
the re-export stays where it was, below the block, with its comment in the present tense.

The sweep reports no misplaced import across the 41 modules now.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

mobile/src/terminal/document/fit-scale.ts

@@ -7,10 +7,10 @@ import {
   updateTransform
 } from './viewport-transform'
 import type { TerminalDocumentScope } from './document-scope'
+import { scheduleDocumentFrame } from './document-frame-registry'
 
 /** The narrowest grid a fit or a text-scale change will fit to. */
 export const MIN_FIT_COLS = 20
-import { scheduleDocumentFrame } from './document-frame-registry'
 
 export function getCellHeight(scope: TerminalDocumentScope) {
   if (!scope.term || !scope.term._core) {

mobile/src/terminal/document/host-notify.ts

@@ -1,9 +1,9 @@
 import type { TerminalDocumentScope } from './document-scope'
+import type { TerminalEngineError } from './document-host-seams'
 
 // Declared beside the seam that hands it out, and re-exported here because this is where the
-// document's readers have always named it.
+// document's readers name it.
 export type { TerminalEngineError } from './document-host-seams'
-import type { TerminalEngineError } from './document-host-seams'
 
 /**
  * The postMessage bridge to the host, and the engine error reporting that rides on it.