fix(circular): skip type-only imports + break tui ↔ overlay-layout cycle

Two changes (one walker, one real code):

1. scripts/check-circular-deps.mjs — skip type-only imports.
   `import type { X } from "..."` and `export type { X } from "..."`
   are erased by tsc at compile time and cannot cause runtime cycles.
   Walker now drops them, matching the precedent set by skipping
   dynamic `await import(...)`. Net effect on full-repo scan:
     before: 9 cycles
     after:  3 cycles (the 6 that disappeared were all `import type`
       false-positives — none were real runtime cycles).

2. packages/tui — break the last 2-file cycle.
   tui.ts and overlay-layout.ts had a real RUNTIME cycle:
     - tui.ts → overlay-layout.ts:  applyLineResets, compositeOverlays,
       extractCursorPosition, isOverlayVisible (4 fns)
     - overlay-layout.ts → tui.ts:  CURSOR_MARKER (1 const)
   Both files already imported `./overlay-types.ts` (no cycle there).
   Moved CURSOR_MARKER from tui.ts into overlay-types.ts and re-exported
   from tui.ts so existing `from "./tui.js"` call sites keep working.
   No behavior change.

Remaining cycles after both fixes (3 real-runtime ones, separate slices):
  - safety/autonomous-rollback chain (9 files, SF extension)
  - packages/coding-agent core mega-cycle (12 files)
  - (one more, see `npm run check:circular`)

These are foundational refactors worth their own commits, not bundled
into this one.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/tui/src/overlay-layout.ts

@@ -12,7 +12,7 @@ import type {
 } from "./overlay-types.js";
 import { tryRender } from "./render-guard.js";
 import { isImageLine } from "./terminal-image.js";
-import { CURSOR_MARKER } from "./tui.js";
+import { CURSOR_MARKER } from "./overlay-types.js";
 import {
 	applyBackgroundToLine,
 	extractSegments,

packages/tui/src/overlay-types.ts

@@ -1,7 +1,19 @@
 /**
  * Overlay sizing, anchoring, and handle types for layered TUI content.
+ *
+ * Also hosts CURSOR_MARKER (moved here from ./tui.ts to break the
+ * tui ↔ overlay-layout circular import — both files already import
+ * this module, so it's the natural shared landing zone).
  */
 
+/**
+ * Cursor position marker — APC (Application Program Command) sequence.
+ * This is a zero-width escape sequence that terminals ignore.
+ * Components emit this at the cursor position when focused.
+ * TUI finds and strips this marker, then positions the hardware cursor there.
+ */
+export const CURSOR_MARKER = "\x1b_sf:c\x07";
+
 /** Margin configuration for overlays */
 export interface OverlayMargin {
 	top?: number;

packages/tui/src/tui.ts

@@ -83,13 +83,11 @@ export function isFocusable(
 	return component !== null && "focused" in component;
 }
 
-/**
- * Cursor position marker - APC (Application Program Command) sequence.
- * This is a zero-width escape sequence that terminals ignore.
- * Components emit this at the cursor position when focused.
- * TUI finds and strips this marker, then positions the hardware cursor there.
- */
-export const CURSOR_MARKER = "\x1b_sf:c\x07";
+// CURSOR_MARKER moved to ./overlay-types.ts to break the
+// tui ↔ overlay-layout circular import. Re-exported here so
+// existing call sites that import { CURSOR_MARKER } from "./tui.js"
+// keep working.
+export { CURSOR_MARKER } from "./overlay-types.js";
 
 export type {
 	OverlayAnchor,