docs: restructure README + add CONTRIBUTING.md + issue templates v1.7.76
- README: group 26 commands into 7 categories, add "Why CCG?" section,
move architecture diagram up, consolidate prerequisites, deduplicate
jq instructions, add "When to change" column for env vars, fold
settings.json and Hook config into <details>
- Add CONTRIBUTING.md with dev setup, PR workflow, commit conventions
- Add .github/ISSUE_TEMPLATE/ (bug report, feature request, good first issue)
- EN and ZH README mirrored (335 lines each, 13 sections)
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5769a1dbe6