fix: rebase workspace-export-from-lockfile onto rattler_lock 0.29

[baszalmstra]

Description

#5989 added pixi workspace export --from-lockfile against an older rattler_lock API. While that PR was open, rattler_lock shipped a refactor that:

• replaced LockedPackageRef with a single LockedPackage enum (and dropped the second _env_data tuple slot on the Pypi variant);
• turned PypiPackageData into a Distribution / Source enum with method accessors (name(), location().inner(), version()), and removed the standalone editable field;
• removed package_record from CondaSourceData (use source.name() instead);
• changed Environment::packages to take rattler_lock::Platform<'lock> instead of rattler_conda_types::Platform.

#5989 was merged without rebasing onto those changes, so main now fails cargo check with seven errors in crates/pixi_cli/src/workspace/export/conda_environment.rs. This PR rebases that one new file onto the current API. Net diff is +29/-11 in a single file.

A few notes on the editable handling, since the lockfile no longer exposes it directly: editability is a manifest concept (the workspace's pixi.toml says editable = true), not a property the resolver writes back. So the new code builds the editable set from environment.pypi_dependencies(Some(*platform)) filtered by spec.editable() == Some(true) and looks each locked pypi package up by name. Transitive pypi source deps that happen to be PypiPackageData::Source are no longer incorrectly rendered with -e.

How Has This Been Tested?

Locally on Windows against the current main@upstream:

• cargo check --workspace --all-targets — clean
• cargo check --workspace --all-targets --features slow_integration_tests,online_tests — clean
• cargo clippy --workspace --all-targets — clean
• cargo fmt --check — clean

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
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Tools: Claude

Checklist:

• I have performed a self-review of my own code