feat(code_runner): rename module, fix __del__ + kernel name, expand tests

- Rename `wrenn.code_interpreter` → `wrenn.code_runner` (canonical).
  Keep old path as deprecation alias that emits a FutureWarning on
  import, mirroring the existing `Sandbox` → `Capsule` pattern.
  Submodule shims `code_interpreter/{capsule,async_capsule,models}.py`
  keep direct-submodule imports working.

- Fix sync/async ctor-failure-safe `__del__`: initialise `_kernel_id`,
  `_kernel_name`, `_proxy_client` before calling `super().__init__` so
  a failed creation no longer crashes the destructor with
  AttributeError.

- Send the kernel name to Jupyter. Previously `POST /api/kernels` had
  no body, so the server picked an arbitrary default kernelspec. Now
  sends `{"name": "wrenn"}` (override via `Capsule(kernel=...)`) and
  reuses an existing kernel only when its `name` matches.

- Preserve Jupyter `text/plain` verbatim in `Result.from_bundle`.
  The previous outer-quote strip was lossy (the string `'2'` became
  indistinguishable from the int `2`, and strings containing escaped
  quotes were mangled). `text` is now the `repr()` Jupyter sends.
  Updated the stale `test_capsule_features` quote-strip test.

- Validate `run_code(language=...)`. Anything other than `"python"`
  now raises `ValueError` instead of being silently ignored.

- Async `__del__` no longer touches the event loop; users must call
  `await close()` or use `async with`.

- New unit suite `tests/test_code_runner_unit.py` (46 tests): MIME
  unpacking, deprecation alias + warning, default template + kernel,
  custom kernel override, ctor-failure-safe __del__, kernel
  create/reuse/cache, retry on 5xx, 4xx propagation, request shape,
  run_code stream/result/error/foreign-parent/idle/unsupported-language,
  async variants.

- New e2e suite `tests/test_code_runner_e2e.py` (44 tests, integration
  marker): template == `code-runner-beta`, kernel == `wrenn`, stdout
  /stderr capture, state/import/function/class persistence, exceptions
  (Value/Name/Syntax), callbacks, multi-line, `text` repr preservation,
  filesystem round-trip, isolation between capsules, deprecated import
  path. MIME-type class covers html, markdown, json, latex, svg,
  javascript, png (matplotlib + seaborn), jpeg, multi-format bundles,
  and text-round-trip via numpy + requests.

- `make test-code-runner` runs unit + e2e together. `make test`
  extended to include the unit file.

- README: "Code Interpreter" section renamed to "Code Runner", all
  imports updated, `kernel=` documented, removed the incorrect
  "quotes stripped automatically" claim, replaced with the actual
  `text/plain` semantics.

- CLAUDE.md: appended a "Code Runner Module" section covering module
  path, defaults, kernel-reuse semantics, lifecycle invariant, and
  the new test files + make target.

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

tests/test_capsule_features.py

@@ -4,7 +4,7 @@ import httpx
 import respx
 
 from wrenn.capsule import Capsule, _build_proxy_url
-from wrenn.code_interpreter.models import Execution, ExecutionError, Logs, Result
+from wrenn.code_runner.models import Execution, ExecutionError, Logs, Result
 
 BASE = "https://app.wrenn.dev/api"
 
@@ -152,10 +152,11 @@ class TestExecutionModels:
         assert r.png == "base64data"
         assert r.is_main_result is True
 
-    def test_result_from_bundle_strips_quotes(self):
+    def test_result_from_bundle_preserves_text_plain(self):
+        # ``text/plain`` is the Jupyter repr — preserved verbatim now.
         bundle = {"text/plain": "'hello'"}
         r = Result.from_bundle(bundle)
-        assert r.text == "hello"
+        assert r.text == "'hello'"
 
     def test_result_from_bundle_extra_mimes(self):
         bundle = {"text/plain": "x", "application/vnd.custom": "data"}