fix(code-runtime-python): capture the error-class constructor and dispatch primitives

The review's remaining items:
- _make_error_class captures Exception and setattr as def-time defaults, so a
  rebind of __main__.Exception/__main__.setattr cannot break the rejection
  constructor.
- dispatch binds _lossless_json_violation, asyncio.get_event_loop, and the
  channel's send method into _run locals before the program runs, so a rebind
  cannot turn a legitimate binding call into an exception or a wall-clock
  timeout.
- The note (en + zh) corrects the stdin coverage phrasing: d3f9f57f5's direct
  EOF-observing case is the in-tree pin, not an approximation.
- Collapse two stray double blank lines in the test file.
Pairing re-recorded.

packages/code-runtime/code-runtime-python/tests/runtime.spec.ts

@@ -750,7 +750,6 @@ describe('PythonCodeRuntime — programs and bindings', () => {
     expect(result.value).toBe('nope')
   }, 15_000)
 
-
   it('still answers the call when the rejection value cannot be converted to a string', async () => {
     // `messageOf` calls `String(error)`, which runs the value's own conversion,
     // and this call site is a DETACHED async reply callback. A rejection whose
@@ -4297,7 +4296,6 @@ describe('PythonCodeRuntime — hostile peer', () => {
     expect(result.value).toBe(8 * chunk.length)
   }, 90_000)
 
-
   it('bounds a flood of zero-byte log lines through the per-entry separator charge', async () => {
     // Blank print() lines carry zero content bytes; without the +1 separator
     // charge they would bypass maxLogBytes entirely and grow the retained