Add proposal cards for new agent actions in chat timeline

client/src/__tests__/agentProposalCards.test.js

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+import React from "react";
+import { fireEvent, render, screen } from "@testing-library/react";
+
+import AgentProposalCard from "../components/chat/AgentProposalCard";
+import { renderAgentTimelineItem } from "../components/chat/renderAgentTimelineItem";
+
+describe("Agent proposal cards", () => {
+  it("renders prioritize_failure_hotspots cards with compact rationale and fields", () => {
+    render(
+      <AgentProposalCard
+        proposal={{
+          type: "prioritize_failure_hotspots",
+          rationale:
+            "Recent runs surfaced unstable boundaries around densely packed synapses, so we should route reviewers to these hotspots first.",
+          focus_metric: "boundary_instability",
+          max_hotspots: 12,
+          dataset_split: "validation",
+        }}
+      />,
+    );
+
+    expect(screen.getByText("Prioritize Failure Hotspots")).toBeTruthy();
+    expect(screen.getByText(/Rationale:/)).toBeTruthy();
+    expect(screen.getByText(/Focus metric:/)).toBeTruthy();
+    expect(screen.getByText(/Max hotspots:/)).toBeTruthy();
+    expect(screen.getByRole("button", { name: "Approve" })).toBeTruthy();
+    expect(screen.getByRole("button", { name: "Reject" })).toBeTruthy();
+  });
+
+  it("renders preview_correction_impact cards and wires action buttons", () => {
+    const onApprove = jest.fn();
+    const onReject = jest.fn();
+    const proposal = {
+      type: "preview_correction_impact",
+      rationale:
+        "Estimate if the correction can reduce merges before applying edits to the shared model state.",
+      target_slice_id: "z-0142",
+      correction_mode: "merge_split_fix",
+      estimated_impact: "-18% merge errors",
+    };
+
+    render(
+      <AgentProposalCard proposal={proposal} onApprove={onApprove} onReject={onReject} />,
+    );
+
+    fireEvent.click(screen.getByRole("button", { name: "Approve" }));
+    fireEvent.click(screen.getByRole("button", { name: "Reject" }));
+
+    expect(screen.getByText("Preview Correction Impact")).toBeTruthy();
+    expect(onApprove).toHaveBeenCalledWith(proposal);
+    expect(onReject).toHaveBeenCalledWith(proposal);
+  });
+
+  it("keeps existing non-proposal timeline rendering unaffected", () => {
+    render(renderAgentTimelineItem({ kind: "assistant", content: "No proposal here." }));
+
+    expect(screen.getByText("No proposal here.")).toBeTruthy();
+  });
+});

client/src/components/chat/AgentProposalCard.js

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+import React from "react";
+import { buildProposalSummary, getProposalCardConfig } from "../../contexts/workflow/proposalCardConfig";
+
+const CARD_STYLE = {
+  border: "1px solid #d9d9d9",
+  borderRadius: 8,
+  padding: 12,
+  marginTop: 8,
+  background: "#fff",
+};
+
+function truncate(text, maxLength = 180) {
+  if (!text) return "";
+  return text.length <= maxLength ? text : `${text.slice(0, maxLength).trimEnd()}…`;
+}
+
+function ProposalSummary({ summary }) {
+  if (!summary.length) return null;
+
+  return (
+    <ul style={{ paddingLeft: 20, margin: "8px 0" }}>
+      {summary.map(({ label, value }) => (
+        <li key={label}>
+          <strong>{label}:</strong> {value}
+        </li>
+      ))}
+    </ul>
+  );
+}
+
+export default function AgentProposalCard({ proposal, onApprove, onReject }) {
+  const config = getProposalCardConfig(proposal?.type);
+
+  if (!config) return null;
+
+  const summary = buildProposalSummary(proposal);
+
+  return (
+    <article style={CARD_STYLE} data-testid={`proposal-card-${proposal.type}`}>
+      <h4 style={{ margin: "0 0 4px" }}>{config.title}</h4>
+      <p style={{ margin: "0 0 8px", color: "#666" }}>{config.description}</p>
+
+      {proposal?.rationale ? (
+        <p style={{ margin: "0 0 8px" }}>
+          <strong>Rationale:</strong> {truncate(proposal.rationale)}
+        </p>
+      ) : null}
+
+      <ProposalSummary summary={summary} />
+
+      <div style={{ display: "flex", gap: 8, marginTop: 10 }}>
+        <button onClick={() => onApprove?.(proposal)} type="button">
+          Approve
+        </button>
+        <button onClick={() => onReject?.(proposal)} type="button">
+          Reject
+        </button>
+      </div>
+    </article>
+  );
+}

client/src/components/chat/renderAgentTimelineItem.js

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+import React from "react";
+import AgentProposalCard from "./AgentProposalCard";
+
+export function renderAgentTimelineItem(message, handlers = {}) {
+  if (message?.kind === "proposal") {
+    return (
+      <AgentProposalCard
+        proposal={message.proposal}
+        onApprove={handlers.onApproveProposal}
+        onReject={handlers.onRejectProposal}
+      />
+    );
+  }
+
+  return <span>{message?.content ?? ""}</span>;
+}

client/src/contexts/workflow/proposalCardConfig.js

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+export const PROPOSAL_CARD_CONFIG = {
+  prioritize_failure_hotspots: {
+    title: "Prioritize Failure Hotspots",
+    description:
+      "Reorders the review queue around high-risk slices with the strongest failure signals.",
+    keyFields: [
+      ["Focus metric", "focus_metric"],
+      ["Max hotspots", "max_hotspots"],
+      ["Dataset split", "dataset_split"],
+    ],
+  },
+  preview_correction_impact: {
+    title: "Preview Correction Impact",
+    description:
+      "Estimates the downstream effect before applying a correction to the active workflow.",
+    keyFields: [
+      ["Target slice", "target_slice_id"],
+      ["Correction mode", "correction_mode"],
+      ["Estimated impact", "estimated_impact"],
+    ],
+  },
+};
+
+export function getProposalCardConfig(proposalType) {
+  return PROPOSAL_CARD_CONFIG[proposalType] ?? null;
+}
+
+export function buildProposalSummary(proposal) {
+  if (!proposal) return [];
+
+  const config = getProposalCardConfig(proposal.type);
+  if (!config) return [];
+
+  return config.keyFields
+    .map(([label, key]) => {
+      const value = proposal[key];
+      if (value === undefined || value === null || value === "") {
+        return null;
+      }
+      return { label, value: String(value) };
+    })
+    .filter(Boolean);
+}