ci: add automated beta SDK release track

[ankita10119]

Changes

Adds an automated beta SDK release track alongside the existing stable track

New files:

• .github/actions/compute-next-version/action.yml - composite action that derives the next version from git tags (no state file needed). For the beta track: latest stable v6.3.0 → v6.4.0-beta.1, auto-incrementing -beta.N on each release. Scopes tag lookups to the current major line by reading .version, so legacy v5 tags are never treated as candidates.
• .github/workflows/beta-autorelease.yml - triggers on PR merge into the beta branch. Computes the next beta version, stamps .version, package.json, src/management/version.ts, and CHANGELOG.md, builds and publishes to npm with --provenance --tag beta, creates a GitHub API-signed release commit (shows as Verified), and publishes a GitHub prerelease. Serialized with a concurrency group to prevent version races.

Modified files:

• .github/workflows/ci.yml - adds beta to push/PR branch triggers so lint, build, test, and coverage run on the beta branch.
• AGENTS.md - documents the beta track workflow for AI coding agents: versioning logic, structured commit message format, files owned by automation, dual-PR requirement for hand-written code.
• CONTRIBUTING.md - documents the beta track for human contributors: consumer opt-in (npm install auth0@beta), the / squash commit message format, and what the automation does end-to-end.

How the two tracks work:

	Stable	beta
branch	master	beta
trigger	Merged release/* PR	Any merged PR into beta
npm tag	latest	beta
version format	v6.4.0	v6.4.0-beta.1

Because v6.4.0-beta.N sorts before v6.4.0 in semver, a plain npm install auth0 never selects a beta version. Consumers must opt in explicitly: npm install auth0@beta

This PR is infrastructure only, it changes nothing on master today and is inert until the beta branch is created and the upstream Fern beta generation target is wired.

References

Testing

• This change adds unit test coverage
• This change adds integration test coverage

Checklist

• I have read the Auth0 general contribution guidelines
• I have read the Auth0 Code of Conduct
• All existing and new tests complete without errors

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.73%. Comparing base (f9d6413) to head (cc7f87e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1394   +/-   ##
=======================================
  Coverage   89.73%   89.73%           
=======================================
  Files         441      441           
  Lines       20799    20799           
  Branches    10146    10146           
=======================================
  Hits        18663    18663           
  Misses       2136     2136           

Flag	Coverage Δ
alltests	89.73% <ø> (ø)

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