Fix audit followups and growth onboarding

[RajjjAryan]

Summary

Closes #67.
Closes #68.
Closes #69.
Closes #70.
Closes #71.
Closes #72.

• tighten personal-data leak scanning to skip user-layer and local environment paths while preserving system-file coverage
• fix stale mode references from data/cv.md and data/article-digest.md to canonical root files
• replace setup clone placeholders and refresh the README project map
• narrow updater docs handling to explicit system-owned docs/assets
• add GitHub-renderable demo/social SVG assets plus a launch checklist
• document template/private-fork/local-clone adoption paths for safer first runs

Verification

• node --test tests/leak-scan-scope.test.mjs tests/repo-contract.test.mjs
• npm test (107 passed, 0 failed, 3 expected no-user-data warnings)
• node -e "import { XMLParser } from 'fast-xml-parser'; import { readFileSync } from 'fs'; const parser = new XMLParser({ ignoreAttributes: false }); for (const file of ['docs/assets/demo-preview.svg','docs/assets/social-preview.svg']) { const parsed = parser.parse(readFileSync(file, 'utf8')); if (!parsed.svg) throw new Error(file + ' did not parse as svg'); console.log(file + ' OK'); }"
• git diff --check