Fix false empty repository reports

[aminhanifm]

What changed

• replace repository-size-only empty detection with positive README and tree evidence
• always request the recursive tree and default-branch check runs, including when GitHub reports size zero
• keep inconclusive, malformed, network, and truncated evidence unknown
• invalidate cached reports with cache schema v2
• add integration coverage for populated size-zero repositories, real empty repositories, and uncertain failures
• add README usage guidance and correct the CSV Health live URL
• add complete social metadata, JSON-LD, a real favicon, and a deterministic 1200 x 630 social image
• prepare the v1.0.0 changelog

Root cause

The collector used repository.size === 0 as an authoritative empty signal before it requested the tree or check runs. GitHub currently reports RepoReady's size as zero despite a populated default branch, so the app manufactured an empty tree and skipped valid evidence.

User impact

RepoReady now detects its own CI, tests, tooling, lockfile, security policy, issue forms, and changelog. Unavailable evidence remains unknown instead of becoming a false failure or empty notice.

Validation

• npm run format
• npm run lint
• npm run typecheck
• npm test (82 tests)
• nested production build at /projects/repo-ready/
• npm run test:e2e (6 browser tests)
• production metadata and 1200 x 630 asset checks
• project scan found no legacy CSV Health URL or em dash