ci: standardize uv version selection across workflows #1094

Priority Level

Low

Task Summary

Standardize uv version selection across GitHub Actions workflows and project configuration so updates follow one clear policy rather than a mix of floating and pinned versions.

Technical Details & Implementation Plan

• Inventory all astral-sh/setup-uv steps and [tool.uv].required-version declarations, including the workspace and e2e project.
• Choose and document one repository-wide version policy and update mechanism. One option is an exact authoritative uv version with setup-uv reading that declaration instead of repeating version: in every job; decide whether the project requirement should remain a compatibility minimum or also serve as the CI pin.
• Apply the chosen convention consistently across test, health-check, Colab, notebook, documentation, and dependency-security workflows.
• Handle Fern workflows that check out repositories into subdirectories: configure setup-uv's working-directory to locate the intended pyproject.toml instead of relying on the default checkout path.
• Preserve independent Python selection for inline scripts; do not introduce an unnecessary UV_PYTHON override as part of uv version selection.

Acceptance criteria:

• CI uv version selection and project compatibility requirements have a documented, consistent relationship.
• Redundant per-job pins or floating-version settings are removed or made consistent with the selected policy.
• Setup resolves the intended uv version for both root and Fern subdirectory checkouts.
• Lockfile checks, dependency audits, the constraints exporter, and representative test/docs validation pass using the selected version. Validate docs without publishing them.
• The process for bumping uv does not require independently updating scattered workflow values.

Investigation / Context

Follow-up to #1093 and Aaron's review thread, including the agreement to handle this separately.

At review time, the repository mixed setup-uv version: "latest" and version: "0.13.4", while project configuration declared required-version = ">=0.13.4". Omitting setup-uv's version while retaining that range selects a matching version; it does not reproduce an exact 0.13.4 pin. Treat the policy choice as explicit rather than assuming removal of workflow pins preserves existing behavior.

Relevant workflows include ci.yml, health-checks.yml, check-colab-notebooks.yml, build-notebooks.yml, docs-preview.yml, build-fern-docs.yml, publish-fern-devnotes.yml, and dependency-security.yml.

Dependencies

No blocker for #1093. Keep this repository-wide cleanup separate from its dependency security changes.