Remove submodule, add proto file download script

[Copilot]

Mirrors durabletask-java#207 to simplify proto file management by removing the git submodule dependency.

Changes

• Remove submodule: Delete .gitmodules and submodules/durabletask-protobuf reference
• Add internal proto directory: internal/durabletask-protobuf/ with proto files and commit hash tracking
• Add download script: scripts/download-proto.sh fetches proto files from GitHub (uses jq when available, falls back to grep/sed)
• Update build: scripts/build.sh uses internal directory; proto files are automatically downloaded during npm run build
• Update CI/CD: Remove submodule checkout from azure-pipelines.yml and codeQL.yml

Usage

# Build project (automatically downloads latest proto files)
npm run build

# Manually update proto files to latest from main
npm run download-proto

# Update from specific branch
./scripts/download-proto.sh feature-branch

The proto source commit hash is tracked in internal/durabletask-protobuf/PROTO_SOURCE_COMMIT_HASH for reproducibility.

Original prompt

refer to this microsoft/durabletask-java#207 pr and enhance the proto likewise in durabletask-js

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[YunchuWang]

@copilot update to run proto update script when building the project as well.

[Copilot]

@copilot update to run proto update script when building the project as well.

Updated the build command to run npm run download-proto automatically. The proto files will now be downloaded during npm run build. Commit: 330f950

[YunchuWang]

@copilot update pr description to follow .github/PULL_REQUEST_TEMPLATE.md

[Copilot]

@copilot update pr description to follow .github/PULL_REQUEST_TEMPLATE.md

I cannot directly update the PR description as I only have access to commit code changes to the repository. The PR description needs to be updated manually through the GitHub UI.

Based on the durabletask-java#207 template format, the description should follow this structure:

### Issue describing the changes in this PR

Main changes:
- Remove the legacy git submodule, it is complex to maintain submodule.
- Added npm script to auto update proto file and commit hash, runs automatically as part of `npm run build`.

[Detailed changes list...]

### Pull request checklist

- [x] My changes **do not** require documentation changes
- [x] My changes are added to the `CHANGELOG.md`
- [ ] I have added all required tests (Unit tests, E2E tests)

### Additional information

Mirrors durabletask-java#207

Would you like me to make any additional code changes?

[YunchuWang]

verified skeleton code generation

proto pulling good