fix: propagate workspace write network access

[jamesjlopez]

Summary

CODEX_CONFIG can now enable network access for workspace-write turns. Previously, the adapter sent networkAccess: false on every prompt and overrode the configured setting. The merge accepts only boolean values, preserves writable roots, and leaves read-only and full-access policies unchanged.

Related: block/buzz#3031

Testing

• npm test (345 passed, 28 skipped)
• npm run typecheck
• npm run build

[BradGroux]

Independent production-path validation from Buzz Desktop 0.5.7 confirms this PR addresses the load-bearing defect, and that the current published adapter remains affected.

Validation from the affected path

• A managed Codex agent received its inbound Buzz mention and started normally.
• Buzz supplied CODEX_CONFIG.sandbox_workspace_write.network_access=true, while the resulting Codex child reported CODEX_SANDBOX_NETWORK_DISABLED=1.
• A read-only Buzz CLI command inside the child failed three out of three times with exit code 2 and the macOS getaddrinfo/EAI_NONAME-shaped error.
• An unsandboxed request to the same hosted relay in the same minute resolved, completed TLS, and returned HTTP/2 403, ruling out host DNS or relay reachability.
• The resulting permission request was rejected by Buzz's unattended fail-closed policy, so no reply could be published.

I also inspected the current npm release, @agentclientprotocol/codex-acp 1.1.14 (gitHead 5faefec5d55ded33c54b68ffec93def4f6c547f5). Its bundle still hardcodes networkAccess: false for Agent mode and only merges writable_roots; upgrading from the affected 1.1.7 installation to 1.1.14 does not fix this path.

The patch here is correctly scoped from static review: it applies the configured value after additional roots are merged, accepts only a real boolean, changes only workspaceWrite, preserves the default false value, and leaves dangerFullAccess unchanged. The added tests cover enabled, absent, invalid, explicit false, preserved roots, and full-access behavior.

I did not rerun this branch's test suite locally; the evidence above is an independent production reproduction plus review of the complete diff. Once this lands, a prompt npm patch release would let Buzz raise its minimum supported adapter version and stop treating affected adapters as healthy.