feat(trace): add diagnosis trace workbench

openspec/specs/mvp-demo-trace-acceptance/spec.md

@@ -1,9 +1,7 @@
 ## Purpose
 
 Provide a repeatable MVP demo flow that can run a chat diagnosis, expose its persisted execution trace, and submit feedback for the same session id.
-
 ## Requirements
-
 ### Requirement: Diagnosis trace can be queried by session id
 The system SHALL expose a read-only HTTP endpoint `GET /api/diagnosis/{sessionId}/trace` that returns the persisted diagnosis trace for the requested session id.
 
@@ -64,3 +62,39 @@ The MVP demo SHALL document which trace fields to inspect for evidence, verifier
 #### Scenario: Checklist maps fields to interview claims
 - **WHEN** a developer reviews a trace response
 - **THEN** the checklist SHALL map concrete JSON paths to the claims made in the interview walkthrough
+
+### Requirement: MVP demo SHALL provide a browser trace workbench
+The MVP demo SHALL provide a browser-accessible static page for inspecting one
+diagnosis trace by session id using the existing read-only Trace API.
+
+#### Scenario: Existing trace renders in the workbench
+- **WHEN** a reviewer opens the Trace workbench with a session id that exists
+- **THEN** the page SHALL request `GET /api/diagnosis/{sessionId}/trace`
+- **AND** it SHALL render session summary, ordered agent steps, ordered tool
+  invocations, verifier evaluation, and final answer when present
+
+#### Scenario: Trace workbench handles missing or failed traces
+- **WHEN** the Trace API returns an error or the session id is empty
+- **THEN** the page SHALL show a clear error or empty state without mutating any
+  diagnosis data
+
+### Requirement: Trace workbench SHALL expose evidence and skill boundaries
+The Trace workbench SHALL make tool evidence and skill-loading boundaries visible
+without requiring raw JSON inspection first.
+
+#### Scenario: Tool and verifier evidence are inspectable
+- **WHEN** a trace includes tool invocations and verifier facts
+- **THEN** the page SHALL show tool invocation counts, success status, tool
+  filters, verifier facts, and evidence references
+
+#### Scenario: RAG details are inspectable for lookup knowledge calls
+- **WHEN** a `lookup_knowledge` invocation includes retrieval details
+- **THEN** the page SHALL show query transform, retrieval trace, context pack,
+  rerank trace, and evidence block data where available
+
+#### Scenario: Skill boundary checks are visible
+- **WHEN** a trace includes planner, executor, or verifier steps
+- **THEN** the page SHALL show best-effort indicators for selected skill,
+  planner `read_skill` text mentions, executor `read_skill` text mentions, and
+  verifier `read_skill` text mentions
+