fix: example avalue pointer bug + CI examples check (v0.5.5)

[kolkov]

Summary

• Fix examples/simple/main.go: avalue elements must be pointers TO argument values, not values directly. Darwin path was correct, Windows/Linux path was not
• Add examples build verification to CI — all examples/*/go.mod compiled in cross-compile job

Bug

// WRONG (crashed on Windows 11 ARM64):
arg := unsafe.Pointer(unsafe.StringData(str))
args := []unsafe.Pointer{arg}                    // value directly ❌

// CORRECT:
cstr := unsafe.Pointer(unsafe.StringData(str))
args := []unsafe.Pointer{unsafe.Pointer(&cstr)}  // pointer TO value ✅

Reported by @lkmavi on Windows 11 ARM64 (Snapdragon).

Test plan

• examples/simple/ compiles locally
• Main module builds and tests pass
• CI green (includes new examples build check)

Closes: reported via chat, no GitHub issue

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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