Release Worktree Grove v0.3.0

[SmartAI]

Summary

• add wtg new BRANCH --enter for a visibly nested interactive shell in the new checkout, launched only after Grove releases its mutation lock
• add fail-closed wtg update / wtg update --check for standard uv and pipx tool installations
• require stable immutable GitHub releases whose title exactly equals the strict vX.Y.Z tag, with per-hop redirect containment, GitHub asset digests, SHA256SUMS, wheel structure/metadata checks, exact manager ownership, bounded execution, and post-install health attestation
• normalize and attest published release titles/assets, and standardize v0.3.0 version sources
• re-record the README GIF and accessible transcript from a real built-wheel --enter workflow

Upgrade note

v0.2.x predates wtg update, so v0.3.0 must be installed once from the verified release wheel. Existing exact required_version = "0.2.0" project pins must then be deliberately changed to 0.3.0; self-update never rewrites repository policy.

Validation

• python3 -m unittest discover -v — 114 passed, 1 skipped
• python3 -m unittest -v tests.test_updater — 18 passed
• WTG_TEST_ARTIFACTS=1 python3 -m unittest -v tests.test_artifacts — passed
• python3 -m build && python3 -m twine check dist/* — passed
• real isolated same-version self-replacement through uv 0.11.28 — passed locally
• real isolated same-version self-replacement through pipx 1.16.6 — passed locally
• PR CI additionally exercises pinned uv 0.12.3 and pipx 1.16.6 on Ubuntu and macOS
• live wtg update --check against GitHub's immutable latest release — passed
• all existing GitHub release names now exactly equal their tags
• compileall, tabnanny, YAML parse, GIF/transcript validation, and git diff --check — passed