feat(workflows): project BPMN diagnostics onto an element-keyed instance overlay

[sfmskywalker]

Closes #1000. Part of elsa-workflows/elsa-core#7909 (W13, Studio half). The core half, which projects interpreter diagnostics into the journal, merged in elsa-workflows/elsa-core#8058.

What changed

The BPMN instance viewer now lights up gateways, events and flows, not only bound tasks. Under the design's Option A, only bound work has an activity id, so the existing activity-keyed stats channel could never show where a token waits at a gateway.

• Contract mirror (Elsa.Studio.Workflows.Core/Domain/Models/Bpmn/): BpmnDiagnosticEventNames and BpmnDiagnosticLogPayload mirror elsa-core's constants and payload one-to-one, with a pointer to the core files as the source of truth.
• One mapping: BpmnElementStatsProjector is the only place diagnostic kinds turn into element stats, keyed by BPMN element id or flow id. Covered states: token present, flow taken, gateway joined, boundary triggered, work completed, cancelled or torn down, and waiting shown as blocked. Entries from nested scopes land in the same map, since BPMN ids are document-unique.
• Refresh: DiagramDesignerWrapper.RefreshElementStatsAsync runs on the same observer tick as activity stats in WorkflowInstanceDesigner. It filters the journal by every BpmnProcess activity id, not by event names, because several kind names collide with generic lifecycle events. It is incremental: a high-water mark per instance and scope set means each tick fetches only new records, folded into the existing map. That is safe because the server orders the filtered journal by a per-instance sequence that survives resumes. Each tick pages at most 10,000 records, and a larger backlog continues on the next tick, so nothing is truncated. The refresh inherits the existing observer disposal (fix(workflows): stop instance designer refresh timers when the circuit disconnects #992); no new timer.
• Plumbing: an optional IBpmnElementStatsSink, implemented only by BpmnDiagramDesigner, forwards through the wrapper and component to the X6 adapter's existing updateBpmnElementStats. IDiagramDesigner is not widened for every designer.
• Rendering: node badges already existed. Edges now render "taken" in the existing badge tone.
• Write-only: nothing is read back into the engine, and no element gains behaviour.

Verification

cd src/modules/Elsa.Studio.Workflows.Designer/ClientLib && npm run check:generated && npm test && npm run build   # 243/243
dotnet build Elsa.Studio.sln --configuration Release                                                                   # 0 errors
dotnet test src/modules/Elsa.Studio.Workflows.Tests --configuration Release --no-build --framework net10.0            # 363/363
dotnet test src/modules/Elsa.Studio.Workflows.Designer.Tests --configuration Release --no-build --framework net10.0   # 83/83

Tests cover:

• The issue's verification scenario, with journal records built exactly as elsa-core writes them: in a parallel split where one branch blocks, the join shows a waiting token, the blocked task shows blocked, and the completed branch's flows show taken.
• Nested-scope folding.
• An incremental refresh fetching only new records.
• A reset when the instance changes.
• A backlog larger than one tick's cap, fully folded across ticks.
• A later record for the same element overriding an earlier one across a refresh boundary, identical to a single pass.
• Wiring into the instance designer's observer.

Review: three iterations on the standards and spec axes, with four must-fix findings resolved: incremental reads, a bounded per-tick catch-up, the cross-boundary test, and internal test seams instead of reflection. Won't-fix: the mirror's details stays nullable, deliberately defensive when reading a payload off the wire.

🤖 Generated with Claude Code

[greptile-apps]

Confidence Score: 5/5

Merge safe.

Summary

• This change projects BPMN journal diagnostics into an element-keyed instance overlay so gateways, events, and sequence flows display runtime state alongside activity statistics.
• It retains overlays across the Blazor and browser-canvas mount lifecycle, including the initial refresh used by finished instances, and adds focused coverage for projection, pagination, refresh, rendering, and mount timing.

_{Reviews (2) · Last reviewed commit: "refactor(workflows): stop discarding the..."}