Fix local folder inconsistencies - require initialization and use symlinked paths

[mrsimpson]

This commit addresses several inconsistencies in how local documentation folders
were handled compared to git repositories:

Changes:

1. Init command now supports local folders

   • Creates symlinks in .knowledge/docsets/{id}/
   • Validates source paths exist
   • Creates .agentic-metadata.json for tracking
   • Counts files and stores metadata

2. Server validates initialization for local folders

   • Checks for .agentic-metadata.json before allowing search
   • Returns consistent error messages for uninitialized docsets
   • Both local folders and git repos now require explicit init

3. Server returns symlinked paths for local folders

   • Local folders now return .knowledge/docsets/{id}/ path
   • Agents no longer need to traverse up to project root
   • Consistent behavior between git repos and local folders

4. Create command updated

   • Removed automatic symlink creation for local folders
   • Added helpful message to run init command
   • Consistent flow: create -> init -> search

5. Core package exports createSymlinks

   • Exported from paths/symlinks.js for use in CLI

Result: Local folders now behave consistently with git repos - both
require initialization via 'agentic-knowledge init {docset_id}' before
they can be searched, and both return paths under .knowledge/docsets/.