Fixes#1055.
## Root cause
`tea notifications --mine` still initialized full repository context before checking the global notification scope, so it probed the current working directory with git and could select or fail on repository-derived context even though repository data is not needed.
## Changes
- Add an InitCommand option to skip local git repository discovery when a command does not need repository context.
- Use that option for notification list and mark-as operations when `--mine` is set.
- Add a regression test that makes `git` fail if invoked and verifies `notifications --mine` still uses the global notifications API.
## Tests
- `go test ./cmd/notifications ./modules/context`
Reviewed-on: https://gitea.com/gitea/tea/pulls/1056
Lunny Xiao