Improve home discovery and All Tools acceptance

[baixiangcpp]

Summary

• replace generic homepage quick category cards with five concrete scenario entry cards for API requests, JWT review, log scrubbing, JSON cleanup, and SVG optimization
• add a home discovery acceptance guard covering homepage CTA/trust/scenario requirements and All Tools progressive disclosure evidence
• document the All Tools hybrid incremental-rendering strategy, DOM budget, and latest /en/all-tools performance budget row

Validation

• npm test -- tests/guards/home-discovery-acceptance.test.ts tests/guards/home-tool-catalog-performance-guard.test.ts tests/guards/home-search-button-performance-guard.test.ts tests/guards/all-tools-performance-a11y-guard.test.ts tests/component/all-tools-discovery.test.tsx
• npm run validate
• npm run build:app
• npm run build:post

Closes #241
Closes #244

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