feat: archive mvp demo trace acceptance

devflow/projects/2026-07-03-mvp-demo-trace-acceptance/brief.md

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+# MVP Demo Trace Acceptance Brief
+
+## Background
+
+- User goal: make the MVP runnable, observable, and explainable for an Agent Engineer interview.
+- Current problem: the system can execute diagnosis, but reviewers need a simple way to replay one session from final answer back to agent steps and tool evidence.
+- Associated OpenSpec: `openspec/changes/mvp-demo-trace-acceptance/`
+- Devflow scale: standard-light.
+
+## Scope
+
+- In scope:
+  - `mvp-demo` Spring profile overlay.
+  - `GET /api/diagnosis/{sessionId}/trace` read-only API.
+  - Trace aggregation DTO/service/controller.
+  - Focused service tests.
+  - Demo and acceptance documentation.
+- Out of scope:
+  - Sensitive configuration cleanup.
+  - Full offline LLM/vector/database mock runtime.
+  - Database schema migration.
+  - Changes to chat execution, verifier routing, upload, or feedback behavior.
+- Impact area:
+  - `src/main/java/com/superbiz/agent/controller`
+  - `src/main/java/com/superbiz/agent/service`
+  - `src/main/java/com/superbiz/agent/dto`
+  - `src/main/resources/application-mvp-demo.yml`
+  - `mvp/demo`
+  - `mvp/notes`
+
+## OpenSpec Alignment
+
+- proposal coverage: covered
+- specs coverage: covered
+- tasks coverage: covered