docs: add Technical Charter and restructure governance documentation

[kriswest]

Description

Adds a Technical Charter (CHARTER.md) and restructures the project's governance documentation to align with the FINOS software-project-blueprint standard.

Key changes:

• CHARTER.md (new) — Defines GitProxy's mission, scope, maintainer structure, IP framework, and amendment process.
• CONTRIBUTING.md (restructured) — Governance content (roles, contribution rules, voting, dispute resolution) added above the existing development guide. Includes a new Cross-Firm Review clause requiring significant changes (new features, breaking changes) to be approved by a maintainer from a different organisation, while explicitly exempting routine maintenance. Adds a Dispute Resolution process (consensus → community meeting → vote → FINOS tie-break).
• website/docs/development/contributing.mdx (slimmed) — Governance content removed; page now focuses on contribution mechanics and links to CONTRIBUTING.md and CHARTER.md for governance details.

This is a governance-only change with no code modifications.

Related Issue

Resolves #1660

Checklist

General

• I have read the CONTRIBUTING.md guidelines
• Commit messages follow Conventional Commits format
• I have a FINOS CLA on file

Documentation

• Documentation has been added/updated for any new features

Configuration

• If configuration schema (config.schema.json) was modified:
  • TypeScript types regenerated (npm run generate-config-types)
  • Schema reference docs regenerated (npm run gen-schema-doc)

Tests

• Tests have been added/updated for new functionality
• Unit tests pass (npm test)
• Linting and formatting pass (npm run lint and npm run format:check)
• Type checks pass (npm run check-types)

[netlify]

✅ Deploy Preview for endearing-brigadeiros-63f9d0 canceled.

Name	Link
🔨 Latest commit	995397b
🔍 Latest deploy log	https://app.netlify.com/projects/endearing-brigadeiros-63f9d0/deploys/6a8c652d20f78000085a079e

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.06%. Comparing base (449f35b) to head (995397b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1664   +/-   ##
=======================================
  Coverage   86.06%   86.06%           
=======================================
  Files         100      100           
  Lines        5548     5548           
  Branches      988      988           
=======================================
  Hits         4775     4775           
  Misses        525      525           
  Partials      248      248           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[andypols]

LGTM Thanks

[kriswest]

We discussed this at the meeting on Monday and had broad approval from those present. In the spirit of its own contents it would be good to get as many maintainer approvals on it as we can. Hence @finos/git-proxy-maintainers please take a look and give this approval before I merge later in the week.

[coopernetes]

Just one minor comment to set the right expectation re: deployment assets.

[jescalada]

LGTM! 👍🏼