chore: EPIC-02 refinement — address non-blocking review comments

[steilerDev]

Summary

Addresses non-blocking observations collected from all EPIC-02 PR reviews (#45, #47, #48, #49) as part of the epic refinement phase.

Code fixes

• Fix trailing space in Sidebar className (PR feat(client): responsive layout and cross-browser compatibility #48, architect observation): The template literal ${styles.sidebar} ${isOpen ? styles.open : ''} produced a trailing space when isOpen was false. Switched to [styles.sidebar, isOpen && styles.open].filter(Boolean).join(' ').

• Wrap splitChunks in isProduction conditional (PR feat: performance baseline with code splitting, compression & cache headers #49, architect observation): splitChunks: { chunks: 'all' } was previously applied in both dev and production modes. While harmless, it's cleaner to only apply it in production alongside the other optimization settings.

Process observations (documented, no code changes)

• CLAUDE.md refinement phase was bundled with Story 2.7: Performance Baseline & Fast Load Time #33 feature PR (scope creep noted by PO)
• Test authorship in Story 2.7: Performance Baseline & Fast Load Time #33 by frontend-developer instead of QA agent (process note by PO)
• Unicode hamburger icon could become SVG in future (architect forward-looking note, PR feat(client): client-side routing and application shell layout (#27) #45)
• request() not exported for potential future PATCH support (PO observation, PR feat(client): API client module (Story #31) #47)

Test plan

• npm run lint — 0 errors
• npm run format:check — all clean
• npm run typecheck — all packages clean
• npm test — 163 tests pass (18 suites)
• npm run build — succeeds
• npm audit — 0 vulnerabilities

🤖 Generated with Claude Code

[github-actions]

🎉 This PR is included in version 1.6.1 🎉

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