feat: eval run command — prepare, execute, collect pipeline

Implement the uwf-eval run <task-dir> command with 3-phase pipeline:

- prepare: read task.yaml, copy fixture/ to temp workdir
- execute: shell out to uwf thread start + exec
- collect: run judges, compute weighted score, store CAS node,
  set @uwf/eval/<task>/latest variable

Changes:
- src/runner/ — types, prepare, execute, collect, index
- src/storage/store.ts — createEvalStore(), setEvalLatest()
- src/commands/run.ts — full pipeline wiring with --agent/--model/--count
- 9 new tests (prepare + collect + weighted scoring)

Builtin judges return placeholder score 0 (Phase 1c).

Refs #70

packages/eval/__tests__/collect.test.ts

@@ -0,0 +1,157 @@
+import { bootstrap, createMemoryStore } from "@ocas/core";
+import { describe, expect, test } from "vitest";
+import type { JudgeRunner } from "../src/runner/index.js";
+import { collect, computeOverall } from "../src/runner/index.js";
+import type { EvalRunConfig, EvalStore } from "../src/storage/index.js";
+import type { JudgeEntry, TaskManifest } from "../src/task/index.js";
+
+function makeJudge(name: string, weight: number, builtin: boolean): JudgeEntry {
+  return {
+    name,
+    weight,
+    builtin,
+    entry: builtin ? null : `dist/judges/${name}.js`,
+    schema: null,
+  };
+}
+
+function makeManifest(judges: JudgeEntry[]): TaskManifest {
+  return {
+    name: "fix-off-by-one",
+    description: "test task",
+    workflow: "solve-issue",
+    prompt: "Fix the bug",
+    limits: { maxSteps: 10, timeoutMinutes: 30 },
+    judges,
+  };
+}
+
+function makeEvalStore(): EvalStore {
+  const store = createMemoryStore();
+  bootstrap(store);
+  return { store, varStore: store.var };
+}
+
+const CONFIG: EvalRunConfig = {
+  agent: "hermes",
+  model: "claude-sonnet-4",
+  engineVersion: "test",
+};
+
+/** Returns a fixed score per judge name. */
+function scriptedRunner(scores: Record<string, number>): JudgeRunner {
+  return async (_taskDir, _workDir, _threadId, judge) => ({
+    score: scores[judge.name] ?? 0,
+    data: { judged: judge.name },
+    schema: { type: "object" },
+  });
+}
+
+describe("computeOverall", () => {
+  test("computes the weighted average correctly", () => {
+    const overall = computeOverall([
+      { score: 0.8, weight: 0.3 },
+      { score: 0.6, weight: 0.3 },
+      { score: 1.0, weight: 0.4 },
+    ]);
+    // 0.24 + 0.18 + 0.4 = 0.82
+    expect(overall).toBeCloseTo(0.82, 10);
+  });
+
+  test("a weight-0 judge does not affect the result", () => {
+    const withInformational = computeOverall([
+      { score: 1.0, weight: 1.0 },
+      { score: 0.0, weight: 0.0 },
+    ]);
+    expect(withInformational).toBe(1.0);
+  });
+
+  test("returns 0 when total weight is 0", () => {
+    expect(computeOverall([{ score: 0.5, weight: 0 }])).toBe(0);
+  });
+});
+
+describe("collect", () => {
+  test("computes weighted score correctly across judges", async () => {
+    const evalStore = makeEvalStore();
+    const manifest = makeManifest([
+      makeJudge("test-pass", 0.6, false),
+      makeJudge("code-quality", 0.4, false),
+    ]);
+    const runJudge = scriptedRunner({ "test-pass": 1.0, "code-quality": 0.5 });
+
+    const result = await collect(
+      {
+        evalStore,
+        taskDir: "/tmp/task",
+        workDir: "/tmp/work",
+        threadId: "THREAD123",
+        manifest,
+        config: CONFIG,
+      },
+      runJudge,
+    );
+
+    // 1.0 * 0.6 + 0.5 * 0.4 = 0.8
+    expect(result.overall).toBeCloseTo(0.8, 10);
+    expect(result.runHash).toBeTruthy();
+    expect(result.judges).toHaveLength(2);
+    expect(result.judges[0]).toEqual({ name: "test-pass", score: 1.0, weight: 0.6 });
+
+    const latest = evalStore.varStore.list({
+      exactName: "@uwf/eval/fix-off-by-one/latest",
+    });
+    expect(latest[0]?.value).toBe(result.runHash);
+  });
+
+  test("handles a judge with weight 0 (informational)", async () => {
+    const evalStore = makeEvalStore();
+    const manifest = makeManifest([
+      makeJudge("test-pass", 1.0, false),
+      makeJudge("token-stats", 0, true),
+    ]);
+    // token-stats is builtin → default runner would score 0; give scripted score
+    // that would skew the result if it were counted.
+    const runJudge = scriptedRunner({ "test-pass": 0.5, "token-stats": 1.0 });
+
+    const result = await collect(
+      {
+        evalStore,
+        taskDir: "/tmp/task",
+        workDir: "/tmp/work",
+        threadId: "THREAD123",
+        manifest,
+        config: CONFIG,
+      },
+      runJudge,
+    );
+
+    // Only test-pass (weight 1.0) counts → overall = 0.5
+    expect(result.overall).toBeCloseTo(0.5, 10);
+    expect(result.judges).toHaveLength(2);
+    const tokenStats = result.judges.find((j) => j.name === "token-stats");
+    expect(tokenStats?.weight).toBe(0);
+  });
+
+  test("builtin judges are skipped with placeholder score 0", async () => {
+    const evalStore = makeEvalStore();
+    const manifest = makeManifest([makeJudge("frontmatter-compliance", 1.0, true)]);
+
+    // Use the default runner (no injected runner) → builtin skipped → score 0.
+    const result = await collect({
+      evalStore,
+      taskDir: "/tmp/task",
+      workDir: "/tmp/work",
+      threadId: "THREAD123",
+      manifest,
+      config: CONFIG,
+    });
+
+    expect(result.overall).toBe(0);
+    expect(result.judges[0]).toEqual({
+      name: "frontmatter-compliance",
+      score: 0,
+      weight: 1.0,
+    });
+  });
+});