fix(core): correct local folder docset initialization path

[mrsimpson]

Intent

Fix critical bug where local folder docsets could not be initialized correctly. The calculateLocalPath() function was returning the source path (e.g., ./docs) for local_folder type docsets instead of the standard docset directory (.knowledge/docsets/{id}). This caused the init command to use the source directory as the target, potentially deleting source files with --force and creating circular symlinks.

Key changes

• calculateLocalPath() now consistently returns .knowledge/docsets/{id} for all source types including local_folder, matching behavior of git_repo and archive types
• Local folder initialization now correctly creates symlinks in the docset directory pointing to source folders, preserving source files
• Updated tests to expect the corrected behavior
• Fixed invalid source type zip to archive in example config
• Added local-docs docset as working example of local folder configuration

Dependencies and side effects

• Existing local folder docsets will need to be re-initialized after this fix
• The symlink structure changes from source-path-based to standard docset directory, ensuring consistency across all source types
• MCP server path resolution for local folders remains compatible as it already uses the standard docset directory path