Add frontend proposal cards for new agent actions

[akgohain]

Motivation

• Render two new agent proposal types (prioritize_failure_hotspots, preview_correction_impact) in the chat timeline with a compact rationale and key fields while preserving existing approve/reject controls.

Description

• Add a focused renderer component client/src/components/chat/AgentProposalCard.js that handles the two new proposal types and delegates unknown types to a fallback renderer so existing UI remains unchanged.
• Centralize title and field mappings in client/src/contexts/workflow/proposalCardFields.js and expose extractKeyFields for compact key-field extraction.
• Add unit tests in client/src/__tests__/agentProposalCards.test.js that cover rendering for both proposal types, the approve/reject button interactions, and fallback behavior for unknown types.
• Add a test script to client/package.json to allow running the required client tests with npm --prefix client test.

Testing

• Ran npm --prefix client test -- --watchAll=false --runInBand agentProposalCards, and the new test suite passed (3 tests, 3 passed).
• Ran npm --prefix client run build, and the production build completed successfully (compiled with unrelated ESLint warnings reported).

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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.