Add workflow timeline actor and event-type filters

[akgohain]

Motivation

• Improve timeline debugging and review by adding actor and event-type filters while preserving the default full timeline view.
• Ensure filtering stays lightweight and performant for long event lists by doing filtering in a memoized provider and keeping the renderer simple.

Description

• Add a memoized timeline context WorkflowTimelineProvider that exposes actorFilter, eventTypeFilter, filteredEvents, setActorFilter, setEventTypeFilter, and clearFilters and normalizes/filtering logic; filtering is computed with useMemo to minimize work for long lists (client/src/contexts/workflow/WorkflowTimelineContext.js).
• Add a lightweight timeline renderer WorkflowTimeline that consumes the provider and renders events as an accessible list, and a WorkflowTimelineFilters component with actor select (all/user/agent/system), event-type text input, and a clear button (client/src/components/workflow/WorkflowTimeline.js, client/src/components/workflow/WorkflowTimelineFilters.js).
• Add unit tests covering default full timeline, actor+event-type combination, clear/reset, and event-type-only filtering (client/src/__tests__/workflowTimelineFilters.test.jsx).
• Add test script to client/package.json so test commands required by CI/local workflow are available (client/package.json).

Testing

• Ran npm --prefix client test -- --watchAll=false --runInBand workflowTimelineFilters and all tests passed (3 passed).
• Ran npm --prefix client run build and the production build completed successfully (build succeeded with ESLint warnings reported during compilation).

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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.