test: cover HttpApi workspace routing middleware

[kitlangton]

Summary

• Add focused Effect-native coverage for HttpApi workspace routing middleware across remote HTTP, remote WebSocket, local workspace context, control-plane routing, fallback directory hints, missing workspaces, and inactive remote sync.
• Keep proxy/routing tests aligned with Effect HttpServer responses and simplify shared test setup.
• Clean up WebSocket echo test helpers to handle binary-capable frame types explicitly.

Tests

• bunx prettier --write packages/opencode/test/server/httpapi-workspace-routing.test.ts packages/opencode/test/server/workspace-proxy.test.ts packages/opencode/test/server/workspace-routing.test.ts
• bunx oxlint packages/opencode/test/server/httpapi-workspace-routing.test.ts packages/opencode/test/server/workspace-proxy.test.ts packages/opencode/test/server/workspace-routing.test.ts
• bun typecheck from packages/opencode
• bun run test -- test/server/httpapi-workspace-routing.test.ts test/server/workspace-proxy.test.ts test/server/workspace-routing.test.ts from packages/opencode
• push hook: bun turbo typecheck