feat: add automatic workspace detection based on file path

[paris3200]

Summary

This PR adds automatic workspace detection that switches to the appropriate workspace when opening markdown files based on their file path.

Changes

• Added auto_detect_workspace() function in workspace.lua that:

  • Checks the current file's absolute path
  • Compares it against all configured workspace vault paths
  • Automatically switches to the matching workspace if found

• Added setup_autocommands() function in init.lua that:

  • Sets up autocommands for BufEnter and BufRead events
  • Triggers workspace detection for all *.md files

Benefits

• Eliminates the need to manually switch workspaces with <leader>nw
• Works seamlessly when editing files across multiple vaults
• Only switches workspaces when necessary (avoids redundant switches)

Testing

Tested with multiple workspaces by opening files from different vault paths and verifying that:

• The correct workspace is automatically selected
• Link following (gf) works correctly across workspaces
• No unnecessary workspace switches occur when already in the correct workspace