refactor(e2e): extract infrastructure into tests/e2e/infra/ module

- Move fixtures.ts, llm-judge.ts, results-db.ts to tests/e2e/infra/
- Deduplicate wdio.conf.js: use createTestFixture() instead of inline copy
- Replace __dirname paths with projectRoot-anchored paths
- Create test-mode-constants.ts (typed env var names, flag registry)
- Create scripts/preflight-check.sh (validates tauri-driver, display, Claude CLI)
- Create scripts/check-test-flags.sh (CI lint for AGOR_TEST flag drift)
- Rewrite tests/e2e/README.md with full documentation
- Update spec imports for moved infra files

tests/e2e/infra/results-db.ts

@@ -0,0 +1,113 @@
+// Test results store — persists test run outcomes as JSON for analysis
+// No native deps needed — reads/writes a JSON file
+
+import { resolve, dirname } from 'node:path';
+import { mkdirSync, readFileSync, writeFileSync, existsSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const DEFAULT_PATH = resolve(__dirname, '../../test-results/results.json');
+
+export interface TestRunRow {
+  run_id: string;
+  started_at: string;
+  finished_at: string | null;
+  status: 'running' | 'passed' | 'failed' | 'error';
+  total_tests: number;
+  passed_tests: number;
+  failed_tests: number;
+  duration_ms: number | null;
+  git_branch: string | null;
+  git_sha: string | null;
+}
+
+export interface TestStepRow {
+  run_id: string;
+  scenario_name: string;
+  step_name: string;
+  status: 'passed' | 'failed' | 'skipped' | 'error';
+  duration_ms: number | null;
+  error_message: string | null;
+  screenshot_path: string | null;
+  agent_cost_usd: number | null;
+  created_at: string;
+}
+
+interface ResultsStore {
+  runs: TestRunRow[];
+  steps: TestStepRow[];
+}
+
+export class ResultsDb {
+  private filePath: string;
+  private store: ResultsStore;
+
+  constructor(filePath = DEFAULT_PATH) {
+    this.filePath = filePath;
+    mkdirSync(dirname(filePath), { recursive: true });
+    this.store = this.load();
+  }
+
+  private load(): ResultsStore {
+    if (existsSync(this.filePath)) {
+      try {
+        return JSON.parse(readFileSync(this.filePath, 'utf-8'));
+      } catch {
+        return { runs: [], steps: [] };
+      }
+    }
+    return { runs: [], steps: [] };
+  }
+
+  private save(): void {
+    writeFileSync(this.filePath, JSON.stringify(this.store, null, 2));
+  }
+
+  startRun(runId: string, gitBranch?: string, gitSha?: string): void {
+    this.store.runs.push({
+      run_id: runId,
+      started_at: new Date().toISOString(),
+      finished_at: null,
+      status: 'running',
+      total_tests: 0,
+      passed_tests: 0,
+      failed_tests: 0,
+      duration_ms: null,
+      git_branch: gitBranch ?? null,
+      git_sha: gitSha ?? null,
+    });
+    this.save();
+  }
+
+  finishRun(runId: string, status: 'passed' | 'failed' | 'error', durationMs: number): void {
+    const run = this.store.runs.find(r => r.run_id === runId);
+    if (!run) return;
+
+    const steps = this.store.steps.filter(s => s.run_id === runId);
+    run.finished_at = new Date().toISOString();
+    run.status = status;
+    run.duration_ms = durationMs;
+    run.total_tests = steps.length;
+    run.passed_tests = steps.filter(s => s.status === 'passed').length;
+    run.failed_tests = steps.filter(s => s.status === 'failed' || s.status === 'error').length;
+    this.save();
+  }
+
+  recordStep(step: Omit<TestStepRow, 'created_at'>): void {
+    this.store.steps.push({
+      ...step,
+      created_at: new Date().toISOString(),
+    });
+    this.save();
+  }
+
+  getRecentRuns(limit = 20): TestRunRow[] {
+    return this.store.runs
+      .sort((a, b) => b.started_at.localeCompare(a.started_at))
+      .slice(0, limit);
+  }
+
+  getStepsForRun(runId: string): TestStepRow[] {
+    return this.store.steps.filter(s => s.run_id === runId);
+  }
+}