fix(coding-agent): added guarded dynamic import shim for worker fallback

- Rewrote dynamic `import(...)` rewriting to emit a guarded callee that prefers `__omp_import__` and falls back to native `import` when the helper is unavailable.
- Added a shared shim constant and updated import-rewrite tests to verify routed dynamic imports work both with the injected helper and after serializing into a realm without it.

docs/tools/eval.md

@@ -125,7 +125,7 @@ Implemented in `packages/coding-agent/src/eval/js/worker-core.ts`, `packages/cod
 - Persistent worker-backed VM sessions keyed by `js:${sessionId}`
 - `reset: true` calls `resetVmContext(sessionKey)` before the cell executes; reset is destructive for all live runs on that JS session
 - Top-level `await` and bare `return` are supported by wrapping code in an async IIFE when `wrapCode()` sees `await` or `return`
-- Top-level static `import ... from ...` and dynamic `import(...)` calls are routed through `rewriteImports()`, which sends them via `__omp_import__` so the specifier resolves against the session cwd
+- Top-level static `import ... from ...` and dynamic `import(...)` calls are routed through `rewriteImports()`, which sends them via `__omp_import__` so the specifier resolves against the session cwd. Dynamic-import call sites are swapped for a guarded shim (`typeof __omp_import__ === "function" ? __omp_import__ : (s, o) => import(s, o)`) rather than the bare helper identifier: functions handed to puppeteer (`tab.evaluate`, `page.evaluate`, ...) are serialized with `Function.prototype.toString()` and re-evaluated inside the browser page, where the worker-injected helper does not exist, so the shim falls back to native dynamic import there
 - Module cache is busted for **local** imports between cells so edits to source files are picked up without restarting the runtime. `__omp_import__` deletes `require.cache[absPath]` before re-importing whenever the original specifier is a filesystem path: relative (`./x`, `../x`, `.`, `..`), POSIX-absolute (`/...`), home-prefixed (`~/...`), or Windows drive-letter (`C:\...` / `C:/...`). Bare specifiers (`react`, `lodash/x`) and URL/scheme specifiers (`node:fs`, `file://...`, `https://...`) are left in cache so package identity stays stable across cells. The cache-bust only fires when the resolved target is an absolute path — unresolved bare-package fallbacks (`resolveImportSpecifier()` returning the original specifier) skip it.
 - The prelude installs globals:
   - `display`, `print`