Improve updates, worktree management, and repository creation

[ashproto]

Summary

• render updater release notes as sanitized Markdown and proactively check on startup, every 30 minutes, and after app activation
• replace the native WebView context menu with app-owned linked-worktree management, including local/upstream state, folder/change actions, and safe removal
• hide the primary checkout from the linked-worktree section while retaining it internally for branch safety
• add local and local-plus-GitHub repository creation from the app and macOS File menu
• treat GitHub creation for an unborn repository as successful after creating the remote and adding origin, deferring the first push until a commit exists

Why

Release notes were displayed as flattened plain text, background update checks did not prompt, worktrees had no management surface, and the primary checkout was presented as though it were another linked worktree. The app also lacked a repository initialization flow, while GitHub repository creation always attempted git push HEAD, which fails for a repository with no commits.

User impact

Users receive readable update prompts without manually checking, can understand and safely manage linked worktrees, can create new repositories without leaving Git It, and can connect an empty repository to GitHub without receiving a false push failure.

Validation

• npm test — 36 files, 327 tests passed
• npm run check — 0 errors and 0 warnings
• npm run build
• cargo test -p git-core — 183 tests passed
• cargo check -p git-it
• rendered production-build QA with no console errors
• git diff --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 756e26947b

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".