chore: add pre-commit hooks + readme/changelog linters, dependency overrides, doc fixes

[imantsk]

Summary

• Add Husky + lint-staged pre-commit flow and two repository linters that auto-fix/validate src/readme.txt and CHANGELOG.md.
• Normalize and auto-fix many documentation-formatting issues; reduce npm audit surface with targeted overrides.
• Fix a few existing README/CHANGELOG formatting problems and make linting idempotent.

Key changes (high level)

• Tooling & hooks
  • Added Husky pre-commit hook (.husky/pre-commit) and prepare script in package.json.
  • Added lint-staged config to run file-type checks on staged files.
• Linters
  • New linters: scripts/linters/lint-readme.ts and scripts/linters/lint-changelog.ts (autofix + validations).
  • Removed old combined scripts/lint-readmes.ts.
• package.json
  • Scripts: lint:readme, lint:changelog.
  • Added husky, lint-staged devDeps (pinned lint-staged@^15.5.2 for current Node), updated lint-staged config.
  • Added safe overrides for several transitive packages to address vulnerabilities & engine mismatches.
• Documentation & fixes
  • CONTRIBUTING.md — instructions for hooks.
  • Auto-fixed formatting in src/readme.txt and CHANGELOG.md.
• Security/deps
  • Ran non-breaking npm audit fix and added targeted overrides (see Risks/Notes).

Behavior / rules enforced

• readme.txt: canonical WordPress header order/format, section/subsection casing rules, list marker normalization, blank-line rules (scoped for changelog).
• CHANGELOG.md: release headers normalized to ## [X.Y.Z] (YYYY-MM-DD), ### change-type headings normalized, list marker normalization, spacing rules (1 blank after #/##, no blank after ###), intelligent conversion of indented sublists.
• Linters are idempotent and auto-stage fixes via lint-staged (hook).

Testing / how to validate locally

1. Install deps & set up hooks:
   • npm install
   • npm run prepare
2. Run linters:
   • npm run lint:readme
   • npm run lint:changelog
   • npx lint-staged
3. Try commit flow:
   • Edit src/readme.txt or CHANGELOG.md, stage and git commit — the hook should auto-fix and re-stage.
4. Audit / smoke tests:
   • npm audit
   • npm run build / npm test:php / npm run test:playwright

Risks / notes

• lint-staged pinned to ^15.5.2 to remain compatible with Node v20.16.0 — recommend upgrading Node to >= 20.17 and then moving to lint-staged 16.x.
• Overrides should be considered temporary; plan to remove them after upstream packages ship fixes.
• Linters change doc text formatting (safe for readme/changelog), may cause small rebase conflicts.