feat(cli): add --clear flag to delete subpages before upload

[geopanther]

Summary

Add --clear flag that recursively deletes all child pages under the specified --parent-id before uploading new content. Useful for CI workflows where you want to ensure a clean slate.

Adapted from iamjackg/md2cf#114 by @stevengoossensB.

Changes

• New CLI flag --clear (requires --parent-id)
• Confirmation prompt before deletion — shows count of top-level children, skippable with --yes/-y
• delete_page() and get_child_pages() added to MinimalConfluence API
• get_child_pages() paginates — follows _links.next to fetch all children (Confluence default limit is 25)
• Handle HTTP 204 no-content responses in _request()
• Recursive deletion with error handling per page

Differences from upstream

• Requires --parent-id — errors explicitly instead of silently doing nothing
• Confirmation prompt with --yes to skip (upstream had none)
• Paginated child page fetching (upstream only got first 25)
• Proper 204 handling in base _request()

Tests (6 new)

• test_delete_subpages_empty_parent — no children, no deletes
• test_delete_subpages_flat_children — direct children deleted
• test_delete_subpages_nested_children — depth-first recursive deletion
• test_delete_subpages_partial_failure — continues on HTTPError
• test_get_child_pages_pagination — follows _links.next
• test_get_child_pages_empty — returns empty list

All 156 unit tests pass.

[geopanther]

Maintainer Review

Verdict: ⚠️ Request changes

The feature is useful for CI workflows, but this is a destructive operation that needs more safeguards before merging.

Blocking concerns:

1. No confirmation prompt — Running --clear with the wrong --parent-id could wipe an entire Confluence subtree. Should add a confirmation prompt (skippable via --yes or --force) or at minimum a dry-run preview showing what would be deleted
2. No tests — The recursive deletion logic should have unit tests mocking the API. Key scenarios: empty parent, nested children, partial failure
3. Pagination missing — get_child_pages() only fetches the first page of results (Confluence API default: 25). Large subtrees will be partially deleted. Need to paginate or use limit=500 + follow _links.next

Non-blocking suggestions:

4. Should log the count of pages to delete before starting
5. Consider --clear as a standalone subcommand rather than a flag, to make the destructive nature more explicit
6. The recursive deletion could hit rate limits on large trees — consider adding a small delay between deletes

Good:

• Requiring --parent-id is correct (upstream silently does nothing)
• 204 handling in _request() is clean and benefits other potential DELETE/PUT operations
• Error handling per page (doesn't abort on single failure)

[geopanther]

Updated — addressed all review feedback:

1. ✅ Confirmation prompt — shows count of top-level children before deletion. Skippable with --yes/-y for CI use
2. ✅ 6 unit tests added covering: empty parent, flat children, nested (depth-first), partial failure, pagination, empty results
3. ✅ Pagination — get_child_pages() now follows _links.next with limit=100 per request, fetching all children regardless of count