<!-- Provide a brief summary of your changes -->
Ensure Go audit-mode interceptors remain non-blocking when validator or
mutator invocation returns an error.
## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
SEP says audit-mode interceptors MUST NOT block execution regardless of
results. The Go SDK already avoided blocking on audit-mode validation
findings, but validator/mutator handler or RPC errors could still abort
unless `FailOpen` was set.
This change makes audit mode consistently non-blocking for invocation
errors as well, matching the existing C# orchestrator behavior where
`isAudit || failOpen` allows execution to continue.
## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->
Added focused Go chain tests covering audit-mode validator and mutator
errors.
## Breaking Changes
<!-- Will users need to update their code or configurations? -->
None. This only relaxes audit-mode error handling to match SEP
semantics.
## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->
C# already treats audit-mode invocation failures as non-blocking. This
aligns the Go chain behavior with that implementation and SEP audit-mode
semantics.
Signed-off-by: Ukjae Jeong <jeongukjae@gmail.com>