feat(agama): add foreign-call code-generation conformance tests for the transpiler

@imran-ishaq is already working on this.

Since Jun 24, 2026.

**Is your feature request related to a problem? Please describe.**
The transpiler's Call (foreign-routine) construct and its exception-capture form (result | error = Call …) are covered
only by syntax-pass tests; nothing asserts they generate the expected action-call code and capture-variable
declaration, so a code-generation regression could go unnoticed.

**Describe the solution you'd like**
Add a test that transpiles a flow with a static Call and the exception-capture form, asserting the generated code
contains the action-call invocation with the target class/method and declares the capture variable.

**Describe alternatives you've considered**
Relying on syntax-pass tests — rejected: they don't verify code generation for foreign calls.

**Additional context**
Part of the effort to add semantic/spec-conformance coverage to the Agama subsystem; covers the
transpiler/code-generation side of Call (runtime invocation is exercised by the engine's end-to-end tests on a
deployment).