Add frontend proposal cards for prioritize_failure_hotspots and preview_correction_impact

[akgohain]

Motivation

• Render two new agent proposal types (prioritize_failure_hotspots and preview_correction_impact) as readable cards in the chat timeline.
• Surface a compact rationale and the most relevant proposal fields so users can quickly assess suggestions.
• Preserve existing approve/reject controls and fallback rendering so current proposal UI remains unaffected.

Description

• Add a proposal content mapper client/src/contexts/workflow/proposalCardConfig.js that detects type/proposal_type, truncates rationale, and selects key fields for each new proposal type.
• Add AgentProposalCard component at client/src/components/chat/AgentProposalCard.js to render title, compact rationale, key fields and keep Approve/Reject buttons.
• Add ChatTimelineMessage at client/src/components/chat/ChatTimelineMessage.js to render AgentProposalCard when item.kind === "agent_proposal" and otherwise render normal messages.
• Add focused tests at client/src/__tests__/agentProposalCards.test.js covering both new proposal types (rendering, rationale truncation) and fallback behavior, and ensure approve/reject callbacks are invoked.
• Add a test script to client/package.json to support the required test command.

Testing

• Ran npm --prefix client test -- --watchAll=false --runInBand agentProposalCards and the suite passed: 1 test suite, 3 tests passed.
• Ran npm --prefix client run build and the production build completed successfully (compiled with unrelated ESLint warnings).

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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.