* feat: add bedrock + vertex optional extras with install docs and import hints (#574)
Declare [project.optional-dependencies] with vertex (google-auth) and
bedrock (boto3) extras so "strix-agent[vertex]" / "strix-agent[bedrock]"
install the provider SDKs. Add an Installation section to the Bedrock docs
mirroring Vertex, and a _provider_import_hint helper in warm_up_llm that
surfaces a pip-install hint when a provider dependency is missing.
Fixes#574, #573
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
* fix(providers): use pipx in install hint to match docs
A pipx-installed strix can't add an extra with 'pip install' (wrong env);
mirror the documented 'pipx install "strix-agent[...]"' command. Addresses
Greptile review.
