Add onboarding to connect repos without remotes

doc/architecture.md

@@ -9,11 +9,15 @@
 - `git-tui`:
   - Initializes and runs the curses application loop.
   - Handles startup bootstrap for non-repository directories.
+  - Handles startup onboarding for repositories without configured remotes.
   - Renders a menu-driven UI with keyboard navigation.
   - Executes Git subprocess commands and displays command output.
   - Executes provider-specific publication for new remote repositories:
     - GitHub via `gh` CLI.
     - Gitea via HTTPS API and token-authenticated initial push.
+  - Executes provider-specific connection to existing remote repositories:
+    - GitHub by resolving owner or URL input to `origin`.
+    - Gitea by resolving owner and base URL or URL input to `origin`.
   - Implements file selection for staged and unstaged operations.
 
 ## Public API and Contracts