Add actor and event-type filters for workflow timeline

[akgohain]

Motivation

• Improve debugging and study review by adding timeline filters for event actor and event type while preserving the default full timeline view.
• Keep rendering performant for long timelines by avoiding unnecessary work when no filters are active.

Description

• Add a reusable filtering utility timelineFilters.js that exports TIMELINE_ACTOR_OPTIONS, DEFAULT_TIMELINE_FILTERS, normalizeTimelineFilters, eventMatchesTimelineFilters, and filterTimelineEvents with a fast-path when no filters are set.
• Add WorkflowTimelineFilters UI component providing an actor dropdown, an event-type text input, and a clear/reset button that calls the provided callbacks.
• Add WorkflowTimeline container component that renders the filter controls and memoizes filtered events using useMemo so filtering recomputes only when events or filters change.
• Add unit tests workflowTimelineFilters.test.js that cover default full-timeline behavior, actor/text filter combinations, and clear/reset interactions.

Testing

• npm --prefix client test -- --watchAll=false --runInBand workflowTimelineFilters failed because this repository's client/package.json does not define a test script (expected fail).
• cd client && npx react-scripts test --watchAll=false --runInBand workflowTimelineFilters passed and reported 3 tests passing for the new suite.
• npm --prefix client run build completed successfully and produced a production build with warnings only.

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Codex Task

[akgohain]

Consolidated into draft PR #165 (feat/codex-wave-integration). Closing this source draft to keep review in one place.