Complete Source Link config: add deterministic build, CI build, and explicit SourceRoot

### Summary

This repository already references `Microsoft.SourceLink.GitHub` and sets `PublishRepositoryUrl` / `EmbedUntrackedSources`, so basic Source Link works. However, it is missing several elements of the canonical Source Link + deterministic-build configuration now standardized across the AWS .NET libraries (see aws/integrations-on-dotnet-aspire-for-aws#245):

- **`true`** — explicit (not relying on the SDK default).
- **CI-gated ``** — currently absent, so CI builds are not path-normalized/fully reproducible and build-agent paths can leak into the PDB.
- **Explicit ``** — needed because the AWS release pipeline packs from a source archive **without a `.git` directory**; without it Source Link cannot derive the repository root and emits no commit-pinned document map.

### Requested change

Bring the build configuration up to the template. Prefer consolidating into a shared `Directory.Build.props` (and `Directory.Packages.props` if using central package management) rather than duplicating across each `.csproj`:

```xml

git
true
true
true
true

```

### Why

Reproducible builds and reliable commit-pinned Source Link for the shipped NuGet packages, consistent with the rest of the AWS .NET library set.

### References

- Canonical template: aws/integrations-on-dotnet-aspire-for-aws#245
- Pipeline build-script revision support: aws/aws-dotnet-devex-pipelines#197

Start by inspecting the repository's Directory.Build.props, Directory.Packages.props, and project files to find the existing Source Link settings and package references. Compare them with the requested template, then validate a CI-style build and package creation. Done means deterministic settings, CI path normalization, and commit-pinned Source Link metadata work for builds from a source archive without .git.

Written by the indexing model from the issue text.