Add WASM target CI jobs for Fastly and Cloudflare adapters

[aram356]

Description

All #[cfg(target_arch = "wasm32")] gated code — including the Cloudflare and Fastly KV store implementations — is invisible to CI. The current CI pipeline only builds and tests on the host triple, meaning compile errors in WASM-only code paths go undetected until deployment.

What needs to be done

Add CI jobs that compile against WASM targets:

• --target wasm32-unknown-unknown for Cloudflare adapter
• --target wasm32-wasip1 for Fastly adapter

These should run cargo check (not cargo test, since tests can't execute under WASM targets) with the appropriate feature flags enabled.

Done when

• CI runs cargo check --target wasm32-unknown-unknown -p edgezero-adapter-cloudflare --features cloudflare
• CI runs cargo check --target wasm32-wasip1 -p edgezero-adapter-fastly --features fastly
• Both jobs pass on main

Affected area

CI / Tooling

Context

Identified during PR #165 (KV store feature) review — the new Cloudflare and Fastly KV implementations are entirely behind #[cfg(target_arch = "wasm32")] and have zero CI coverage.