chore: migrate monorepo from Yarn Classic to Yarn Berry

[mrgrain]

This migrates the monorepo from Yarn Classic (v1) to Yarn Berry (v4.13.0) by enabling the yarnBerry: true option in projenrc.

Yarn Classic has been in maintenance mode for years and Yarn Berry is the actively developed version. The migration is needed to stay on a supported package manager and to unblock future improvements that depend on Yarn Berry features, such as better workspace dependency resolution and the yarn dlx command.

The actual change is a single line in .projenrc.ts. Everything else is the result of running npx projen with the updated cdklabs-projen-project-types (^0.3.21) and projen (^0.99.38) which now support Yarn Berry monorepos.

The nodeLinker: node-modules setting in the new .yarnrc.yml files ensures that Yarn Berry continues to use the traditional node_modules layout. This means the migration should be transparent to all packages and their consumers — no code changes are required, only the tooling around dependency installation and workspace commands changes.

Notably, the Yarn Classic nohoist configuration in the root package.json is replaced by installConfig.hoistingLimits: workspaces in the packages that previously needed it (cloud-assembly-schema and cloud-assembly-api). This is the Yarn Berry equivalent and achieves the same isolation of bundled dependencies.

CI workflows are updated to use corepack enable before setup-node (so that the packageManager field in package.json is respected) and all yarn install flags are updated from the Classic syntax (--check-files, --frozen-lockfile) to the Berry equivalents (--no-immutable, --immutable). Task definitions in .projen/tasks.json switch from yarn workspaces run to yarn workspaces foreach --all --exclude . --topological-dev run and from npx to yarn dlx where appropriate.

Checklist

• This change contains a major version upgrade for a dependency and I confirm all breaking changes are addressed
  • Release notes for the new version:

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.29%. Comparing base (2a848bc) to head (8b2f363).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1321      +/-   ##
==========================================
+ Coverage   88.20%   88.29%   +0.08%     
==========================================
  Files          73       73              
  Lines       10386    10386              
  Branches     1409     1414       +5     
==========================================
+ Hits         9161     9170       +9     
+ Misses       1198     1189       -9     
  Partials       27       27              

Flag	Coverage Δ
suite.unit	88.29% <ø> (+0.08%)	⬆️

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