Task 267: Fix stale test counts in tech-overview body text

Status: DONE

Problem

The tech-overview.md summary table (line 24) has correct test counts (2,635 = TS 2,044 + Rust 377 + E2E 214), but the body text paragraphs are stale:

• Line 184: "2,353のテスト" → should be 2,635
• Line 189: "TypeScript ユニットテスト (1,922件)" → should be 2,044
• Line 190: "Playwright E2E テスト (139件)" → should be 214

Solution

1. Fix the stale numbers in the body text
2. Add article content validation tests to prevent future drift between the summary table and body text

Acceptance Criteria

• [ ] Body text matches summary table
• [ ] Article content validation tests check consistency
• [ ] All tests pass