feat: scaffold go backend foundation

.planning/phases/001-go-backend-foundation-and-workflow-boundary/001-SUMMARY.md

@@ -0,0 +1,55 @@
+# Phase 1 Summary
+
+**Status:** Complete
+**Completed:** 2026-04-26
+
+## Delivered
+
+- Initialized Go backend module.
+- Added `cmd/tutor-api` entrypoint.
+- Added app assembly package.
+- Added environment-backed config with defaults for:
+  - HTTP address
+  - environment
+  - workflow runtime path
+  - model key defaulting to `deepseek-v4-flash`
+  - third-one binary path
+- Added HTTP health endpoint at `GET /healthz`.
+- Added typed workflow boundary and stub runner.
+- Added tests for config, health endpoint, and workflow stub behavior.
+- Updated `AGENTS.md` with concrete Go validation commands.
+
+## Files Added
+
+- `go.mod`
+- `cmd/tutor-api/main.go`
+- `internal/app/server.go`
+- `internal/config/config.go`
+- `internal/config/config_test.go`
+- `internal/httpapi/handler.go`
+- `internal/httpapi/handler_test.go`
+- `internal/workflows/contracts.go`
+- `internal/workflows/runner.go`
+- `internal/workflows/runner_test.go`
+
+## Verification
+
+```powershell
+gofmt -w cmd internal
+go test ./...
+openspec validate bootstrap-job-tutor-platform --strict
+```
+
+All checks passed.
+
+Go source line-count check passed; no manually authored Go file exceeds 600
+lines.
+
+## Deferred
+
+- Real diagnostic interview workflow execution.
+- Persistence.
+- Auth.
+- Live third-one execution.
+- Frontend.
+- Ontology and asset generation.