Astrid-owned I/O: replace wasi:io with astrid:io@1.0.0 (error / poll / streams)

[joshuajbouw]

Summary

Replaces the wasi:io dependency in the host ABI with an Astrid-owned astrid:io@1.0.0 package (three interfaces: error, poll, streams). The host ABI is now fully self-contained — no wasi:* surface anywhere — so every host call routes through Astrid's audit, capability, cancellation, and per-principal quota layers without exception. This is also what makes the hermit-rs unikernel target viable: the WIT contract stays stable, and the kernel-side impl swaps from wasmtime-wasi-backed futures to native unikernel primitives.

Context: this amendment edits @1.0.0 files

This PR modifies host/{net,http,process,sys}@1.0.0.wit in place rather than shipping @1.1.0 variants. One-shot pre-adoption amendment, justified because:

• The @1.0.0 freeze landed on main in feat!: split astrid:capsule@0.1.0 into per-domain frozen packages #7 without any downstream consumer.
• The kernel scaffolding is still in WIP (see unicity-astrid/astrid#feat/wit-per-domain-split); no SDK or capsule has bound to the @1.0.0 shapes.
• The dependency change (wasi:io → astrid:io) is structural enough that doing it as @1.1.0 evolution would force every kernel + SDK to register dual versions of four packages forever, for no downstream benefit.

The frozen-file CI gate has been retired in commit 8a0f29d — it was tripping on the legitimate pre-adoption amendments and providing no consumer protection (no consumers exist yet). The freeze rule remains documented in the README; re-enable the check from git history once a real downstream consumer ships against a versioned file.

Commits

1. 9d71a05 fix!: replace wasi:io/poll with astrid:io/poll@1.0.0

   • New host/io@1.0.0.wit with the pollable resource and poll(list<borrow<pollable>>) -> result<list<u32>, error-code>.
   • host/{ipc,net,http,process}@1.0.0.wit: use wasi:io/poll@0.2.0.{pollable} → use astrid:io/poll@1.0.0.{pollable}.
   • host/sys@1.0.0.wit: header rewritten — no wasi:* carve-outs.

2. cfe24c0 chore(deps): drop vendored wasi-io

   • Removes deps/wasi-io/ entirely.
   • scripts/validate-wit.sh + .github/workflows/lint.yml comments updated.

3. 0b66ee2 feat(io)!: add astrid:io/error + astrid:io/streams

   • host/io@1.0.0.wit extended with two more interfaces matching the wasi:io@0.2.0 shape (error / poll / streams).
   • Stream halves wired into resources where they pull weight:
     • host/net@1.0.0.wit: tcp-stream.{read-stream, write-stream} — primary throughput primitive for capsule-hosted TCP servers / proxies.
     • host/http@1.0.0.wit: http-stream.body-stream — HTTP response body forwarding.

4. 13daba9 fix(process)!: drop stream halves on process-handle; mark package desktop-only

   • process-handle stays byte-oriented (write-stdin / read-logs); no stream accessors.
   • Reasoning: IPC bus already handles capsule-to-capsule throughput, hermit-rs has no fork/exec model, write-stdin/read-logs covers MCP-stdio and tool capture.

5. 8a0f29d fixup(io): apply Gemini review + drop immutability CI gate

   • poll() per-call cap raised from 64 → 256 (a capsule at full IPC subscription quota was already past 64).
   • input-stream.read() no longer claims to trap above 1 MiB — wasi-style, only traps on lengths exceeding wasm32's addressable range; the host's 1 MiB ceiling truncates the return instead.
   • output-stream.blocking-write-and-flush() and blocking-write-zeroes-and-flush() no longer cap at 4 KiB. The host segments large transfers internally and yields between chunks.
   • Retired scripts/lint-wit-immutability.sh + the WIT frozen-file immutability workflow job (see "Context" above).

Why Astrid-owned and not wasi:io

Even though pollable.block and streams.read look like they're "just plumbing," the wasmtime-wasi implementation skips:

• Cancellation: a capsule unloading mid-block strands the host task on a future that may never complete.
• Audit: every read / write / poll / block / splice is invisible to the audit log.
• Per-principal accounting: no quota dial on pollable / stream handles, no rate limit on poll-loop spam.
• Cross-capsule isolation: relies entirely on the wasmtime ResourceTable boundary, no Astrid-side reinforcement.

Owning the namespace lets the kernel wrap every operation in the same gates that cover astrid:fs, astrid:net, etc. The wasmtime-wasi-io storage types (DynPollable, IoError, DynInputStream, DynOutputStream) are still reused on the desktop kernel — they're futures, not syscalls — but the Host traits themselves are Astrid's, with audit + cancel + quota wrappers around each call. On hermit-rs, those storage types swap for native unikernel wait/io primitives; the WIT contract is unchanged.

Test plan

• scripts/validate-wit.sh passes on all 13 host packages locally (wasm-tools 1.245.1).
• Downstream kernel (unicity-astrid/astrid#feat/wit-per-domain-split) builds clean against this branch (cargo build --workspace, cargo clippy --workspace -- -D warnings).
• CI: WIT files parse job passes.

Downstream

• unicity-astrid/astrid#feat/wit-per-domain-split consumes this branch via the wit submodule. Once this merges, that PR rebases on the new submodule pointer and is ready for review. Kernel-side MAX_POLL_LIST = 64 will be bumped to 256 in a follow-up commit on that branch to match the new WIT.
• SDK and capsules are unaffected by this PR specifically.

[gemini-code-assist]

Code Review

This pull request replaces the external wasi:io dependency with a native astrid:io implementation to ensure all I/O operations are audited, principal-scoped, and quota-bounded within the Astrid kernel. The changes include the introduction of the astrid:io WIT package and updates to http, net, ipc, and process interfaces to utilize these new primitives. Feedback focuses on several restrictive limits in the new I/O implementation: the 64-pollable limit is noted as inconsistent with IPC quotas, the 1 MiB trap on reads is flagged as non-standard, and the 4 KiB caps on blocking write/flush operations are identified as unnecessarily restrictive and potentially inefficient.