uv: declare workspace sources at root (fix geodude build in CI, #74)

[siddhss5]

Fixes #74. Candidate fix for the pre-existing uv sync failure (Failed to build geodude → mj-viser is not a workspace member).

Diagnosis

• uv 0.11.18 (CI's setup-uv@v5) regression vs 0.7.3: it validates a member's workspace = true sources while building that member, and rejects them when the workspace source mapping isn't declared at the root.
• The virtual root pyproject.toml declared no [tool.uv.sources] — each member declared its own — so building geodude failed.
• Not reproducible on macOS (lock + member wheel builds succeed); reproduces only on the Linux CI runner with 0.11.18.

Fix

Declare the full member source map ({ workspace = true }) at the workspace root. Resolution is unchanged locally (uv.lock identical), so this is non-breaking.

Verification is on this PR's CI: if the integration job gets past the geodude build step, the fix holds.

[siddhss5]

Closing — root-level sources were a misdiagnosis. The real root cause (confirmed via CI probe) is that the gitlink directories are empty in CI: actions/checkout runs with submodules: false and there's no .gitmodules, so mj_viser/ada_assets/ada_mj/etc. are empty placeholders; setup.sh's [ ! -d ] guard then sees the dir exists and skips cloning, leaving empty uv members → 'mj-viser is not a workspace member'. The uv sources are fine once the dirs are populated. Fixing in setup.sh (clone unpopulated gitlink dirs). See #74.