Python: Hyperlight: thread-confine sandbox, skip parsing on host callbacks, schema/tool cleanup (#5424)

* improved parsing of tool call results and tweaks

* Address PR review: skip_parsing flag, broader registry close, comment fix

- FunctionTool.invoke now takes a boolean skip_parsing flag instead of the
  SKIP_PARSING sentinel; the sentinel is still accepted as result_parser at
  construction time to opt out of parsing for every call. The two paths are
  equivalent.
- _SandboxRegistry.close now invokes any sandbox close/shutdown hook on the
  entry's own worker thread (PyO3 unsendable), then shuts the worker down,
  then cleans up the per-entry temporary directories.
- Clarified the _SandboxWorker.shutdown comment to describe the actual
  ThreadPoolExecutor.shutdown(wait=False, cancel_futures=False) semantics.
- Hyperlight host callback uses skip_parsing=True (the new flag).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Drop redundant 'is not SKIP_PARSING' guard that mypy 1.x flags

After callable(configured_parser) the sentinel is already excluded; the extra
identity check tripped mypy's non-overlapping identity warning.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fixed sandbox working on copy of tool

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

python/packages/hyperlight/README.md

@@ -130,3 +130,9 @@ codeact = HyperlightCodeActProvider(
 - `allowed_domains` accepts a single string target such as `"github.com"` to
   allow all backend-supported methods, an explicit `(target, method_or_methods)`
   tuple such as `("github.com", "GET")`, or an `AllowedDomain` named tuple.
+- Tools registered with the sandbox return their native Python value
+  (`dict`, `list`, primitives, or custom objects) directly to the guest via the
+  Hyperlight FFI. Any `result_parser` configured on a `FunctionTool` is
+  intended for LLM-facing consumers and does not run on the sandbox path —
+  apply formatting inside the tool function itself if you need it for
+  in-sandbox consumers.