Add Preview 3 draft conformance fixtures and selected official suite coverage

[medz]

Summary

Add draft Preview 3 fixtures and selected upstream coverage so the implementation can be regression-tested against the current component-model and WASI RC sources.

Parent tracking issue: #70
Suggested implementation order: 13 / 14

References

• https://github.com/WebAssembly/WASI/blob/main/docs/Preview2.md
• https://github.com/WebAssembly/component-model/tree/2e4800866d529aedc1b7730bc9452a4f85b97d8f/test
• https://github.com/WebAssembly/wasi-clocks/tree/v0.3.0-rc-2025-09-16/test
• https://github.com/WebAssembly/wasi-random/tree/v0.3.0-rc-2025-09-16/test
• https://github.com/WebAssembly/wasi-filesystem/tree/v0.3.0-rc-2025-09-16/test
• https://github.com/WebAssembly/wasi-sockets/tree/v0.3.0-rc-2025-09-16/test
• https://github.com/WebAssembly/wasi-cli/tree/v0.3.0-rc-2025-09-16/test

Acceptance criteria

• The test suite includes draft Preview 3 fixtures that exercise the async component foundation plus the selected RC packages.
• Where upstream tests are reusable, they are either imported directly or mirrored closely enough to catch semantic drift.
• Verification covers native, web, and node runtime paths at the level each backend claims to support.

[coderabbitai]

🔗 Related PRs

#3 - fix: spec loop typing regression and add doom smoke guard [merged]
#4 - test: decouple fixture tests from example and remove isolate overhead [merged]

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