✨ feat: add fork environment support

[SigureMo]

Summary

• add a dedicated meowda fork / meowda env fork command and remove fork-specific flags from create
• split create and fork workflows in the CLI and VenvService, with fork mechanics moved into src/venv/fork.rs
• rename the former backend layer to venv and update the README examples and command reference

Closes #59.

Testing

• cargo +stable fmt --all
• cargo +stable clippy --all-targets --all-features -- -D warnings
• cargo +stable test

^{This PR is driven by @copilot (gpt-5.4 xhigh)}

[Copilot]

Pull request overview

This PR refactors the “fork environment” workflow into a dedicated CLI command (meowda fork / meowda env fork), splitting create vs fork logic in the service layer and moving fork mechanics into a new src/venv/fork.rs module.

Changes:

• Introduce meowda fork / meowda env fork commands and wire them into the CLI entrypoint.
• Split VenvBackend into VenvService, extracting venv creation into src/venv/create.rs and fork implementation into src/venv/fork.rs.
• Update scope handling and documentation/examples to reflect the new commands and module layout.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/venv/mod.rs	Renames backend to VenvService, adds create/fork APIs with option structs, and hooks into new fork module.
src/venv/fork.rs	New fork implementation: resolves source env/executable, creates target venv, copies site-packages/scripts, rewrites paths, adds tests.
src/venv/create.rs	New helper to run uv venv with consistent flags.
src/store/venv_store.rs	Makes ScopeType Copy to support reuse across CLI/service flows.
src/main.rs	Rewires entrypoint to venv::VenvService and new fork command routes.
src/cli/mod.rs	Exposes new cli::fork module.
src/cli/fork.rs	Implements meowda fork command handler and invokes VenvService::fork.
src/cli/env.rs	Updates env subcommands to use VenvService and new CreateOptions.
src/cli/args.rs	Adds Fork command and ForkArgs, updates CreateArgs python handling.
src/cli/install.rs	Renames backend parameter usage to VenvService.
src/cli/link.rs	Renames backend parameter usage to VenvService.
README.md	Documents meowda fork usage and updates command reference.

Comments suppressed due to low confidence (1)

src/cli/args.rs:89

• Same default_value = "false" issue as CreateArgs::clear: this may turn --clear into an option that expects an explicit boolean value, instead of a simple flag. Remove the default_value (or set action = clap::ArgAction::SetTrue) so meowda fork ... --clear works as intended.

    #[arg(
        short,
        long,
        default_value = "false",
        help = "Clear existing virtual environment"
    )]
    pub clear: bool,

---

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[Copilot]

clear: bool flags already default to false with clap derive. Setting default_value = "false" can change the argument into a value-taking option (potentially requiring --clear <true|false>), which would break the documented --clear usage. Drop default_value and keep this as a simple presence flag (or explicitly set action = clap::ArgAction::SetTrue).

[Copilot]

include_system_site_packages is computed as pyvenv.cfg exists && (prefix != base_prefix || ...), which will be true for most virtual environments (since sys.prefix != sys.base_prefix). This will cause create_with_source to pass --system-site-packages when forking from a normal venv, unintentionally exposing system packages. Compute this field strictly from pyvenv.cfg's include-system-site-packages value (and keep any "is venv" detection as a separate boolean if needed).

Suggested change

	include_system_site_packages: prefix.join("pyvenv.cfg").exists()
	&& (prefix != base_prefix || !real_prefix.is_empty() || include_system_site_packages),
	include_system_site_packages,

[Copilot]

On Windows, symlink_dir vs symlink_file needs the correct is_dir value. Here link_is_dir is derived from fs::metadata(source) (follows the link) and falls back to false on error, which will mis-handle broken dir symlinks and can make the fork fail. Consider resolving link_target relative to the symlink's parent and checking metadata on that path, or attempting symlink_dir then symlink_file (or vice versa) when the target can't be inspected.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reject self-fork before deleting an existing target env

When fork is called with --clear, the target environment is removed before we validate that the source and target are different. If a user runs something like meowda fork myenv --from myenv --clear (or points --from at the same path), this branch deletes myenv and then create_with_source later aborts on the same-source check in src/venv/fork.rs, resulting in destructive data loss instead of a clean validation error. The source/target identity check should happen before remove_venv is executed.

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