fix: remove non-deterministic uv flags from docs workflow

[Copilot]

The docs CI workflow was passing -U --prerelease=if-necessary-or-explicit to uv sync, bypassing uv.lock pinning and allowing pre-release packages — making every docs build non-reproducible and a potential supply-chain risk.

Changes

• .github/workflows/python-docs.yml: Strip -U --prerelease=if-necessary-or-explicit from extra-args; retain only --all-packages

# Before
extra-args: "--all-packages -U --prerelease=if-necessary-or-explicit"

# After
extra-args: "--all-packages"

Testing

• Not run (why?)
• uv run poe check
• Other: YAML-only change; no code logic affected

Checklist

• Linked issue or task reference
• Added/updated tests where relevant
• Updated docs/README if needed
• No secrets or sensitive data added
• Considered backward compatibility and deployment impact

Additional context

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