[hyperlight_component_util] Expose the fallibility of calls to the host API

[syntactically]

Previously, the generated bindings code for the host side of a component interface would panic in a number of situations if something went wrong while trying to call into the guest. This is undesirable when building hosts that should be reliable in the face of malicious guests that manage to crash the guest partition.

This commit changes the host-side bindgen to wrap the return types of guest calls in a Result wrapper, making it easier to deal with these errors gracefully.

[Copilot]

Pull request overview

This PR updates the host-side WIT bindings generation so that calls from the host into the guest become explicitly fallible, avoiding panics when a malicious or crashing guest causes call failures. It does this by introducing a polarity-aware CallResult<T> wrapper that becomes anyhow::Result<T> for host-to-guest calls, and then threading that through generated signatures and call sites.

Changes:

• Add Positivity::CallResult<T> and use it to wrap host-to-guest call return types (including instantiate).
• Update host bindgen codegen to propagate errors (?) instead of panicking on bad guest returns / lock poisoning.
• Extend the test WIT world + guest implementation with a deliberate trap and add a host test validating the call returns an error.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/tests/rust_guests/witguest/src/main.rs	Adds a guest export (failable.will_trap) that deliberately panics to simulate a trapping guest.
src/tests/rust_guests/witguest/guest.wit	Extends the test world with a new exported failable interface used to exercise fallible host calls.
src/hyperlight_host/tests/wit_test.rs	Updates existing host tests for Result-wrapped guest calls and adds a trap/error assertion test.
src/hyperlight_component_util/src/rtypes.rs	Emits function and instantiate return types as <P as Positivity>::CallResult<T> for polarity-aware fallibility.
src/hyperlight_component_util/src/host.rs	Updates generated host-side bindings to return CallResult and to propagate errors instead of panicking.
src/hyperlight_common/src/component.rs	Introduces Positivity::CallResult<T> and defines it as anyhow::Result<T> for Positive (host calling guest).

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