Adapting meteor pkgs for TypeScript 7

[italojs]

Summary

This PR prepares Meteor applications, generated skeletons, and E2E coverage for the TypeScript 7 migration.

• pins React E2E fixtures and generated skeletons to react-meteor-data@4.1.0-beta.1, which is compatible with TS7
• updates the affected fixtures and locks to typescript@7.0.2
• removes the obsolete forced TypeScript 7 override in the ECMAScript regression app
• adds opt-in branch overrides for internal and external Examples E2E sources, so CI for PRs targeting typescript-changes-consolidated uses the TS7 branches while released Meteor versions retain their existing sources
• supports branch names containing / when cloning an internal example from a GitHub tree URL
• prevents the examples catalog cache from being reused across different example refs

Context

This is part of the consolidated TypeScript 7 migration:

• TypeScript 7 compiler update: Update TypeScript to 7.0.2 #14670
• TS7-compatible react-meteor-data beta: meteor/react-packages#497
• TS7-compatible react-meteor-accounts beta: meteor/react-packages#498
• Staged TS7 examples: meteor/examples#49
• Staged Simpletasks migration: fredmaiaarantes/simpletasks#24
• Staged Meteor Rspack example migration: meteor/meteor3-react#3

The external app branches are consumed only by CI for the TypeScript migration. They can be merged into their own repositories later, without exposing TypeScript 7 constraints to users of released Meteor versions before then.

Validation

• formatting and linting pass
• unit coverage verifies that an offline cache from main is not used for a different examples branch
• the TS7 meteor create --example flow and the internal --from example paths pass end-to-end
• the external simpletasks and meteor3-react source branches pass their respective meteor create --from flows
• full local Examples E2E result: 10 passed, 0 failed