fix: CLI UX improvements and cleanup

[Iamrodos]

This PR bundles several small, related improvements focused on CLI usability and code quality. They're grouped together because:

1. Issues Backup of private organization does nothing, no errors #72, --all-starred does not backup anything #225, and Skipping .. since it's not initialized? #73 all address cases where the CLI behaviour is confusing or silent when users expect feedback
2. The test and docs changes are minor cleanup items that don't warrant separate PRs
3. All changes are low-risk and independently reviewable via separate commits

Commits

• aba048a - fix: warn when --private used without authentication
• 6e2a7e5 - fix: --all-starred now clones repos without --repositories
• 58ad1c2 - docs: fix RST formatting in Known blocking errors section
• b80049e - test: add missing test coverage for case sensitivity fix
• 1d6d474 - fix: improve error messages for inaccessible repos and empty wikis

Details

Issue #72 - Warn when --private used without auth (aba048a)

When users specify --private without providing authentication (token or username/password), the tool would silently return no private repos. As discussed in #72, the agreed approach was to warn rather than error. Now it warns:

The --private flag has no effect without authentication. Use -t/--token, -f/--token-fine, or -u/--username to authenticate.

Issue #73 - Improve error messages for inaccessible repos (1d6d474)

The "not initialized" message was confusing users. It appeared when:

• A wiki is enabled on a repo but has no content (most common)
• A repo is empty, private, or has credential issues

Now shows clearer messages:

• Wiki: Skipping {repo} wiki (wiki is enabled but has no content)
• Other: Skipping {repo} (repository not accessible - may be empty, private, or credentials invalid)

Issue #225 - --all-starred now clones repos (6e2a7e5)

Previously, --all-starred only retrieved the list of starred repos but wouldn't clone them unless --repositories or --all was also specified. Users expected --all-starred alone to clone their starred repos.

As noted in #225, this was identified as "an easy change" - now --all-starred will clone starred repositories without needing additional flags.

RST formatting fix (58ad1c2)

Fixed the "Known blocking errors" section where a single-item numbered list was rendering awkwardly.

Test coverage (b80049e)

Added missing unit tests for the case sensitivity fix (PR #456) and new tests for the --all-starred behaviour.