sync: retargeting a barrel's re-export (export { foo } from './a' -> './b') leaves importers on the old module #2978

When a barrel's re-export points at a different module, sync() leaves the importers bound to the old module.

// a.ts  export function foo(){ return 1 }
// b.ts  export function foo(){ return 2 }
// index.ts  export { foo } from './a';
// c.ts  import { foo } from './index'; export function bar(){ return foo(); }

Index, change index.ts to export { foo } from './b';, then sync().

A reviewer run also found that export * from retargeted the same way and a scoped (watcher) sync behave the same, while a Python __init__.py re-export retarget converges. I re-ran only the named-re-export case above.

Reproduced on main at 77ee348, Linux/WSL2, Node 22.23.2, CODEGRAPH_KERNEL=0.

#2744 and #2665 cover a barrel that gains a name. Here an export that already resolved changes its source. Since c.ts didn't change and index.ts declares nothing that c.ts's edge targets, nothing marks c.ts's import for re-resolution.

Expected. When a file's re-export clauses change, re-resolve the references in files that import through it, as the gained-name case already does.