MGS1048: a layers entry magus cannot honor

layers on magus\project({...}) maps a workspace-relative directory, or a glob of directories, to a layer name. The knowledge graph stamps that name on each directory, magus query "layer=<name>" filters by it, and magus\layer(name) returns every directory in it.

This code fires when an entry cannot be honored:

• the directory does not exist, or the glob matches no directory;
• the path escapes the workspace;
• the layer name is blank or not a lowercase slug (^[a-z][a-z0-9-]*$);
• one directory is declared under two layer names.

Why

A layer that silently covers nothing reads as a boundary the tree keeps when nothing checks it. The load stops so the declaration and the tree agree.

Resolution

The message names the entry and the cause.

• A moved or deleted directory. Point the entry at the directory's new path, or delete the entry.
• A glob that matches nothing. Check the pattern against magus ls and the tree; a glob matches directories, not files.
• A malformed name. Use a lowercase slug such as handler or transport.
• Two names for one directory. Keep one; a directory sits in one layer.