Add back event history legend and auto refresh

[laurakwhit]

Description & motivation 💭

• Adds back the event history legend that was removed with changes in feat(workflow): split Event History into Timeline and Event History tabs #3109. This PR adds back the legend in /timeline view and adds an event type legend to the Event Type column in the table in /history view. It also improves accessibility for the category icons by adding a title prop that describes the event type.
• Adds the auto refresh UI update to the /timeline view.

Screenshots (if applicable) 📸

Timeline	Event History

Design Considerations 🎨

Testing 🧪

How was this tested 👻

• Manual testing
• E2E tests added
• Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

Checklists

Draft Checklist

Merge Checklist

Issue(s) closed

Docs

Any docs updates needed?

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Project	Deployment	Actions	Updated (UTC)
holocene	Ready	Preview, Comment	Feb 25, 2026 4:35pm

[temporal-cicd]

Warnings

⚠️

📊 Strict Mode: 23 errors in 6 files (2.1% of 1113 total) src/lib/components/event/event-summary-row.svelte (5) L131:6: Argument of type 'string | undefined' is not assignable to parameter of type 'string'. L168:23: Parameter 'event' implicitly has an 'any' type. L180:30: Parameter 'group' implicitly has an 'any' type. L180:37: Parameter 'hoveredEventId' implicitly has an 'any' type. L313:16: Type 'ITimestamp | null | undefined' is not assignable to type 'ITimestamp'. src/lib/components/event/pending-activity-summary-row.svelte (5) L116:12: 'event.attempt' is possibly 'null' or 'undefined'. L123:12: 'event.attempt' is possibly 'null' or 'undefined'. L130:13: 'event.attempt' is possibly 'null' or 'undefined'. L132:12: Type 'ITimestamp | null | undefined' is not assignable to type 'ITimestamp'. L143:8: Type 'string | undefined' is not assignable to type 'string | Record<string, unknown> | IPayloads'. src/lib/components/event/pending-nexus-summary-row.svelte (1) L117:16: Type 'ITimestamp | null | undefined' is not assignable to type 'ITimestamp'. src/lib/components/lines-and-dots/svg/timeline-graph-row.svelte (7) L100:20: 'distance' is possibly 'null'. L100:31: 'workflowDistance' is possibly 'null'. L111:20: 'distance' is possibly 'null'. L111:31: 'workflowDistance' is possibly 'null'. L151:29: 'activityTaskScheduled.attributes.attempt' is possibly 'null' or 'undefined'. L244:12: 'pendingActivity.attempt' is possibly 'null' or 'undefined'. L287:13: 'activityTaskScheduled' is possibly 'undefined'. src/lib/layouts/workflow-history-layout.svelte (2) L225:2: Type 'string | undefined' is not assignable to type 'string'. L226:2: Type 'string | undefined' is not assignable to type 'string'. src/lib/layouts/workflow-timeline-layout.svelte (3) L119:20: Type 'WorkflowExecution | null' is not assignable to type 'WorkflowExecution'. L125:14: 'workflow' is possibly 'null'. L126:9: 'workflow' is possibly 'null'.

Generated by 🚫 dangerJS against 7c5fde4

[rossedfort]

Only thought is whether the refresh_off URL search param makes sense. I think it's better than frozen, but it might make the code easier to reason about if the param is flipped, eg. auto_refresh=true. Otherwise lgtm.