[SCcagg5]

Part of a stack of 31 pull requests that depend on each other. They must be reviewed and merged in order: each PR builds on the previous one and its diff only contains its own changes.

• Previous: PR 19
• Next: PR 21

All PRs of the stack

#	PR
1	specs: Add spec 083 and the samples store
2	ir: Add run state fields for ephemeral runs and reused outputs
3	runtime: Bound continuous steps and carry outputs of selected steps
4	api: Add step samples, events, availability and selected-step runs
5	test(ui): add YAML fixtures for the document model tests
6	ui(lib): add shared UI kit, status helpers and right-panel shell
7	ui(canvas): add canvas engine core, toolbars and editor helpers
8	ui(i18n): add workspace message catalogs, first batch
9	ui(canvas): add canvas Flow view, step run panel and workflow panel
10	ui(editor): add YAML document model, canvas model and run source logic
11	ui(editor): Add edit session, YAML format and quick fixes, run actions, tab strip
12	ui(editor): Add canvas graph model, Add step panel, issues popover, run bar
13	ui(canvas): Add layered layout, dependency edges, status styles, reference picker
14	ui(canvas): Add export, flow builder, upstream data panel, output capture
15	ui(canvas): Add node cards, launchers, inspector sections, client issues
16	ui(editor): Add visual editor, step inspector and YAML file panel
17	ui(lists): Open runs on the workflow page; add tab and schedule helpers
18	ui(workspace): Add workspace URL state, legacy redirects and run list links
19	ui(workspace): Add workspace data layer, run facts and Workflow panel
20	ui(workspace): Add run start controls, visible runs and reuse source
21	ui(workspace): Add data provider, bar identity, continuous panel and step list
22	ui(logs): Add run actions cluster, cached logs and log popout page
23	ui(workspace): Add Activity dock, step run view and workflow page
24	test(workspace): Add integration tests for the workspace shell and step view
25	ui(pages): Retire classic run pages and open runs on the workflow page
26	test(editor): Add integration tests for the editor, inspector and run overlay
27	test(ui): Add repository-wide guard tests and ESLint boundary rules
28	e2e: Add workspace helpers and fixtures, update existing specs
29	e2e: Add workspace specs, part 1 of 2
30	e2e: Add workspace specs, part 2 of 2
31	examples: Add the workspace demo workflows

Stack 20/31. Base branch: stack/19-ui15. Review and merge in order; this PR builds on the previous one.
Size: 32 files changed, 7696 insertions(+), 350 deletions(-).
Checked: Typecheck (tsc) of the whole UI and the unit tests of this PR (Vitest), on top of the previous PR.

Summary

This PR adds the run split button and start context, label chips, the visible-runs hook, the run timeline model, and useReuseSource, which picks the earlier run that a step run takes its outputs from. It also moves the Start dialog and DAGActions onto a lazy, profile-aware form.

Why

The bar must start a whole run or one step, and the timeline must pick which runs to show. Step runs that reuse earlier outputs need a clear rule for the source run. This PR builds on the data layer of PR 19. PR 21 wires the data provider and adds the Activity step list. PR 22 adds the run actions.

Changes

Counts: 4 existing files modified, 28 new files (13 tests).

• Bar: RunSplitButton, RunStartContext (one owner of the Start dialog, with requestStart), LabelChips with useWorkflowLabels (each label opens the filtered list).
• Data: useWorkspaceRun (selected run, pinned patches), useVisibleRuns (count or range, test runs, cached time, stored in localStorage), useWorkspaceRefresh (settleAll), sameContent (content equality for SWR copies).
• Timeline: dock/runTimelineModel.ts (bars, lanes, axis scale, counts 5 to 30).
• Step run: step/useReuseSource (picks the source run and checks cached runs, with request limits), visual-editor/run/runSourceChoice.ts (auto, cache or a named run), StepDeclared, StepFactsLine.
• Hosts and guards: RunLinksHost, EditorLeaveGuard (unload, link click, Back and Forward), useLegacyHistoryRedirect (old History index to a run id), canvas/useOpenStepDetails.
• StartDAGModal and DAGActions are reworked: lazy form load, useProfiles hook, only, markActions, startIconOnly props.

How to review

1. step/useReuseSource.ts with runSourceChoice.ts.
2. data/useWorkspaceRun.ts and useVisibleRuns.ts.
3. dock/runTimelineModel.ts.
4. bar/RunStartContext.tsx and RunSplitButton.tsx.
5. DAGActions.tsx and StartDAGModal.tsx.

Most attention: useReuseSource (the rule for the source run and its request limits), and useWorkspaceRun (pinned run and local patches against server data).

Tests

• New: RunStartContext, LabelChips, useVisibleRuns, runTimelineModel (large), useReuseSource, StepDeclared, WorkflowTabsPanel, EditorLeaveGuard, useLegacyHistoryRedirect, runSourceChoice, useProfiles.
• Updated: DAGActions, StartDAGModal.

Screenshots

These components are used by PR 21 and later. The screenshots show the Start dialog and a step run that reuses earlier outputs.