feat: WASM import path — (import "bar" :exec executor)

[lthibault]

Parent

Part of #272 (Glia import system)

Summary

Implement the WASM import path: (import "bar" :exec executor) resolves /lib/bar.wasm, spawns a WASI process via the provided executor capability, bootstraps a Cap'n Proto RPC capability over data_streams, and returns it to the caller.

Scope

• Extend import.rs resolution to handle .wasm extension (falls through from .glia)
• Parse :exec keyword arg from import form
• Error if .wasm resolved but no :exec provided
• Spawn WASM process via executor's Dispatch call
• Bootstrap Cap'n Proto capability over data_streams channel (NOT stdio)
• Return capability reference (Val) to caller
• Default 30s bootstrap timeout, configurable via :timeout keyword arg
• Support absolute /ipfs/-prefixed paths for WASM modules

Non-goals

• Multi-process data_streams (protocol extension — separate work)
• Import caching (TODOS.md)
• Connection rate limiting (TODOS.md)

Test cases (from design doc)

• (import "chess" :exec executor) → capability returned, (perform chess :move ...) works
• .wasm without :exec → error
• WASM module that never exports bootstrap → timeout after 30s (or custom :timeout)
• Both .glia and .wasm exist → .glia wins
• WASM handler crash during bootstrap → clean error, process killed
• /ipfs/-prefixed absolute WASM import

Dependencies

• PR feat: RpcListener/RpcDialer capability-mode subprotocol pair #270 (RpcListener/RpcDialer) — for Cap'n Proto RPC infrastructure
• data_streams protocol extension for multi-process support
• Glia import sub-issue (shared resolution pipeline)