Sketch the Numax host API in WIT - skeleton files + minimal docs

[lntutor]

Summary

• add three independent, parseable WIT packages for database, logging, and GCounter capabilities
• keep the definitions explicitly exploratory with no runtime or SDK wiring
• document current status, validation, and open migration, world, error, value, and versioning questions

Verification

• wasm-tools component wit wit/numax-db.wit
• wasm-tools component wit wit/numax-log.wit
• wasm-tools component wit wit/numax-crdt.wit
• cargo test --workspace -q (498 passed)
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• git diff --check

Closes #61

[lntutor]

Current head ccdbbf9566e9ff33af9239ca265d1b8a62e38781 is mergeable and the visible CI surface on this exact SHA is fully green: cross-platform Check, Clippy, and Test jobs on Ubuntu, macOS, and Windows; Format; Build WASM Examples; CLI Multi-process Smoke; Benchmark Comparator Tests; Ubuntu Profiling Artifacts; Benchmark Regression Gate; and the aggregate CI Success check all completed successfully. There are no review threads or review-body comments open on the current PR state, so if this Numax host API documentation still matches the intended direction, it looks ready for maintainer review/merge when convenient.

[GianIac]

Really like this, it's exactly the kind of concrete starting point I was hoping for.
The 7 open questions in a way that will actually drive the discussion forward (special appreciation for explicitly addressing the aggregated-world trade-off instead of silently picking a side).

I'm going to leave this one open for now, as soon as we start working on the WIT version of the host API, this is the first thing we pick back up. Thanks a lot for the groundwork.