requirements for removing non-buildable buildings from blueprints

docs/requirements.md

@@ -227,7 +227,7 @@ The screen is divided into three vertical sections:
 
 - REQ-UI-BLUEPRINT-PANEL: The blueprint panel is shown to the right of the build button grid. It contains, from top to bottom: a "Create Blueprint" button, a "Delete Blueprint" button, and a list of blueprint buttons (one per saved blueprint, in creation order).
 
-- REQ-UI-BLUEPRINT-CREATE: The "Create Blueprint" button is enabled only when one or more buildings are currently selected. When clicked, a modal dialog appears prompting the player to enter a name. The dialog has Confirm and Cancel buttons. Clicking Cancel closes the dialog with no effect. Clicking Confirm with a non-empty name creates a blueprint from the current selection and appends its button to the blueprint list.
+- REQ-UI-BLUEPRINT-CREATE: The "Create Blueprint" button is enabled only when at least one player-placeable building (i.e. a building with a button in the build button grid) is currently selected; non-player-placeable buildings (HQ, defence stations) in the selection do not count toward this condition. When clicked, a modal dialog appears prompting the player to enter a name. The dialog has Confirm and Cancel buttons. Clicking Cancel closes the dialog with no effect. Clicking Confirm with a non-empty name creates a blueprint from the current selection, silently excluding any non-player-placeable buildings, and appends its button to the blueprint list.
 
 - REQ-UI-BLUEPRINT-STORAGE: A blueprint stores its name and, for each building in the selection, the building type, its rotation, and its tile offset (integer dx, dy) from the center of the bounding box of all selected buildings' footprints. This structure maps directly to a TOML representation (e.g. one `[[building]]` array entry per constituent building).