fix: handle new map Instruction variants in wit-bindgen-core 0.56 (supersedes #190)

[arcjet-rei]

Summary

Supersedes #190. This branch contains the same wit group bump (wit-bindgen-core 0.53.1 → 0.56.0, wit-component 0.245.1 → 0.246.2, wit-bindgen 0.53.1 → 0.56.0) plus the codegen changes required to make it compile.

wit-bindgen-core 0.56 adds first-class map<K,V> support (bytecodealliance/wit-bindgen#1562, #1583), which introduces five new Instruction variants. Gravity's match inst { ... } in cmd/gravity/src/codegen/func.rs is intentionally non-exhaustive-free (no _ => arm) so upstream additions break the build rather than silently emit wrong Go.

New variants handled:

• GuestDeallocateMap { .. } — joined to the existing "gravity doesn't generate the Guest code" group alongside GuestDeallocateList, etc.
• MapLower { .. }, MapLift { .. }, IterMapKey { .. }, IterMapValue { .. } — collapsed into a single todo!("implement instruction: {inst:?}") arm. Gravity has no Go map codegen yet; if a WIT world with map<K,V> is ever fed in, this panics with a clear variant name (same pattern used for FutureLower, StreamLower, etc.).

Test plan

• cargo build --locked — clean
• cargo test --locked — passes
• Built all example wasm with cargo build -p example-* --target wasm32-unknown-unknown --release
• cargo test --locked --test cli — all 8 snapshot tests pass (no drift from wit-component 0.246)
• cd examples && go generate ./... && go test ./... — all Go e2e tests against wazero pass
• CI green on this PR

Once this merges, #190 can be closed.

🤖 Generated with Claude Code

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Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	cargo/​wit-bindgen@​0.53.1 ⏵ 0.56.0
	cargo/​wit-bindgen-core@​0.53.1 ⏵ 0.56.0
	cargo/​wit-component@​0.245.1 ⏵ 0.246.2

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Action	Severity	Alert  (click "▶" to expand/collapse)
Warn		Environment variable access: cargo macro-string Location: Package overview From: ? → cargo/wit-bindgen@0.56.0 → cargo/macro-string@0.2.0 ℹ Read more on: This package | This alert | What is environment variable access? Next steps: Take a moment to review the security alert above. Review the linked package source code to understand the potential risk. Ensure the package is not malicious before proceeding. If you're unsure how to proceed, reach out to your security team or ask the Socket team for help at support@socket.dev. Suggestion: Packages should be clear about which environment variables they access, and care should be taken to ensure they only access environment variables they claim to. Mark the package as acceptable risk. To ignore this alert only in this pull request, reply with the comment @SocketSecurity ignore cargo/macro-string@0.2.0. You can also ignore all packages with @SocketSecurity ignore-all. To ignore an alert for all future pull requests, use Socket's Dashboard to change the triage state of this alert.

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