✨ feat: default create to Python 3.14

[SigureMo]

Summary

• change meowda create to default to Python 3.14 when -p/--python is omitted
• update the CLI help text and README command reference to match the new default
• align the release workflow build matrix with Python 3.14

Validation

• cargo run -- create --help
• 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

Updates Meowda’s create command to use Python 3.14 as the default interpreter when -p/--python is not provided, and aligns user-facing documentation and release CI accordingly.

Changes:

• Default meowda create Python version changed from 3.13 → 3.14.
• Updated CLI help text and README command reference to reflect the new default.
• Updated GitHub Actions build/release workflow matrix to use Python 3.14.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/venv/mod.rs	Switches the internal default Python version used when --python is omitted to 3.14.
src/cli/args.rs	Updates create command help text to state default Python is 3.14.
README.md	Updates command reference to show -p optional and documents the 3.14 default.
.github/workflows/build-and-release.yml	Updates build matrix to run wheel builds against Python 3.14.

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