# Description

This PR removes the `bicep-types` git submodule and migrates
JavaScript/TypeScript package management from npm to pnpm. The
`bicep-types` dependency is now fetched as a git dependency and built
via a `postinstall` script, simplifying the developer experience.

**Key changes:**
- Remove the `bicep-types` git submodule and `.gitmodules` file
- Migrate from npm (`package-lock.json`) to pnpm (`pnpm-lock.yaml`) for:
  - `typespec/`
  - `hack/bicep-types-radius/src/generator/`
  - `hack/bicep-types-radius/src/autorest.bicep/`
- Update GitHub workflows to use pnpm instead of npm
- Update devcontainer configuration for pnpm
- Update Makefiles and build scripts
- Add migration guide for developers with existing clones
- Add a root `package.json` to ensure dev dependencies are at consistent
versions and updated with dependabot.

## Type of change

- This pull request is a minor refactor, code cleanup, test improvement,
or other maintenance task and does not change the functionality of
Radius (issue link optional).

## Testing

1. Checkout the PR branch
2. Follow the contributing guide included with this PR at
`docs/contributing/bicep-types-migration-guide.md`.

## Contributor checklist
Please verify that the PR meets the following requirements, where
applicable:

- An overview of proposed schema changes is included in a linked GitHub
issue.
    - [ ] Yes <!-- TaskRadio schema -->
    - [x] Not applicable <!-- TaskRadio schema -->
- A design document PR is created in the [design-notes
repository](https://github.com/radius-project/design-notes/), if new
APIs are being introduced.
    - [x] Yes <!-- TaskRadio design-pr -->
    - [ ] Not applicable <!-- TaskRadio design-pr -->
- The design document has been reviewed and approved by Radius
maintainers/approvers.
    - [ ] Yes <!-- TaskRadio design-review -->
    - [x] Not applicable <!-- TaskRadio design-review -->
- A PR for the [samples
repository](https://github.com/radius-project/samples) is created, if
existing samples are affected by the changes in this PR.
    - [ ] Yes <!-- TaskRadio samples-pr -->
    - [x] Not applicable <!-- TaskRadio samples-pr -->
- A PR for the [documentation
repository](https://github.com/radius-project/docs) is created, if the
changes in this PR affect the documentation or any user facing updates
are made.
    - [ ] Yes <!-- TaskRadio docs-pr -->
    - [x] Not applicable <!-- TaskRadio docs-pr -->
- A PR for the [recipes
repository](https://github.com/radius-project/recipes) is created, if
existing recipes are affected by the changes in this PR.
    - [ ] Yes <!-- TaskRadio recipes-pr -->
    - [x] Not applicable <!-- TaskRadio recipes-pr -->

**Related PRs:**
- Design document:
radius-project/design-notes#138

---------

Signed-off-by: Brooke Hamilton <45323234+brooke-hamilton@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Dariusz Porowski <3431813+DariuszPorowski@users.noreply.github.com>
Co-authored-by: Sylvain Niles <sylvainniles@microsoft.com>