docs: codify stable release promotion

[abhipillai]

Summary

Documents the stable release promotion process, including:

• reconciling main back into beta before promotion because squash merges create divergent history
• validating the beta prerelease and npm Trusted Publishing before promoting
• mapping patch, minor, and major releases to the corresponding Conventional Commit PR titles
• requiring the beta → main release PR to be squash merged
• removing the obsolete script that pushed directly to main

Verification

• Prettier passed using the existing binary from /Users/apillai/Development/web-sdk/node_modules/.bin/prettier
• git diff --check passed
• Full npm tests were not rerun because registry access is blocked by corporate dependency-confusion controls; this is a documentation/process-only change

Does this close any currently open issues?

No.

• Individual Contributor License Agreement (CLA) signed

Generated with Amp