Preserve notebook workspace dependency context

[farhan-syah]

Workspace notebooks lose inherited dependencies when Venus generates isolated Cargo projects. Resolve notebook dependency context before generation so internal workspace crates remain available.

Closes #5.

What changed

• crates/venus-core/src/compile/notebook_manifest/: Resolve package and workspace dependencies with correct path origins. Preserve aliases, sources, targets, optional features, and root patches.
• crates/venus-core/src/compile/universe/ and production.rs: Share resolved dependency context across generated runtime and standalone projects. Refresh universe caches and loaded cell libraries after local dependency changes.
• crates/venus/cli/src/executor/ and crates/venus-server/src/session/: Share manifest discovery and refresh context during reloads. Split oversized files by responsibility.
• crates/venus-core/tests/workspace_dependencies.rs, crates/venus/cli/tests/workspace.rs, and crates/venus-server/src/session/tests.rs: Cover execution, standalone builds, source refresh, and manifest changes.
• crates/venus-core/src/compile/cell/: Include source and dependency hashes in library filenames. Check refreshed values while retaining loaded libraries.
• Generated Cargo manifests preserve native Windows paths. Path assertions use canonical paths across platforms.
• docs/cells.md: Document workspace notebook dependencies and override behavior.

Checks

cargo fmt --all
cargo clippy --workspace --all-targets -- -D warnings
cargo +stable test --workspace --quiet
cargo doc -p venus-core --no-deps

• CI: Windows, macOS, and Ubuntu tests pass. Formatting and Clippy pass.
• Cargo.toml: 323 tests pass. Eighteen existing tests and doctests remain ignored.
• crates/venus-core: Documentation builds with ten pre-existing rustdoc link warnings.