Move authoring LSP into a cell

[fasterthanlime]

Summary

• move the authoring LSP implementation out of the ddc binary into a dedicated cell
• add the authoring LSP Vox proto crate and wire ddc lsp through the cell loader
• expose the dodeca library surface needed by the cell and keep the pasted LSP tests in integration-tests

Testing

• cargo fmt --all
• cargo check --workspace --all-targets --message-format=short
• cargo nextest run --workspace --no-fail-fast
• cargo shear
• cargo clippy --workspace --all-targets --all-features -- -D warnings