Delete the dead layer-expansion pair in tp-layer

tp--expand-layer-to-props-list and tp--expand-props-to-remove were an
orphaned early draft of "expand a layer name into the property keys it
contributes": nothing calls them - the only reference in the whole
tree (sources, tests, doctest, README) is the pair calling each other.
The maintained equivalent of this logic is the inline expansion in
tp-ops's tp--remove-property, which is what tp-remove actually runs;
if deduplication is ever wanted, that copy is the one to extract.

Keeping a second, uncalled implementation of layer expansion around
invites the two to drift apart silently, so remove the 67 dead lines.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tp-layer.el

@@ -132,74 +132,6 @@ The error message names the full cycle, e.g. \"a -> b -> a\"."
                       (reverse (cons layer-name tp--layer-expansion-stack))
                       " -> "))))
 
-(defun tp--expand-layer-to-props-list (layer-name str start)
-  "Expand LAYER-NAME to a list of property keys it contributes.
-If LAYER-NAME is a layer defined in `tp-layer-alist', returns a list
-of the property keys that the layer adds, plus `tp-name'.
-STR and START are used to get the argument value for parameterized layers.
-For non-layer symbols, returns a list containing just that symbol."
-  (if (tp--is-layer-name-p layer-name)
-      (let* ((existing-props (text-properties-at start str))
-             (existing-tp-name (plist-get existing-props 'tp-name))
-             (layer-prop-value (plist-get existing-props layer-name))
-             ;; Proceed if tp-name matches OR if the layer property exists
-             ;; (for cases where layer was used in mixed syntax without tp-name)
-             (layer-props
-              (cond
-               ;; tp-name matches - traditional layer application
-               ((eq existing-tp-name layer-name)
-                (cond
-                 ;; Parameterized layer - get property keys it would produce
-                 ;; We pass dummy args (t) since we only need the key
-                 ;; names, not values
-                 ((tp-layer-parameterized-p layer-name)
-                  (tp-layer-props-with-args
-                   layer-name
-                   (make-list (length (tp-layer-arglist layer-name)) t)
-                   nil)) ; include-tp-name=nil
-                 ;; Non-parameterized layer
-                 ((assoc layer-name tp-layer-alist)
-                  (tp-layer-props layer-name nil)) ; include-tp-name=nil
-                 ;; Layer group
-                 ((assoc layer-name tp-layer-groups)
-                  (when-let ((layer-props-list (tp-group-props layer-name t)))
-                    (tp--build-layer-props layer-props-list)))))
-               ;; Layer property exists (mixed syntax like `tp-set str 'face 'bold 'layer arg`)
-               ;; In this case, the layer's face properties are merged into face
-               (layer-prop-value
-                (cond
-                 ((tp-layer-parameterized-p layer-name)
-                  (tp--layer-props-for-arg-value layer-name layer-prop-value nil))
-                 ((assoc layer-name tp-layer-alist)
-                  (tp-layer-props layer-name nil))
-                 ((assoc layer-name tp-layer-groups)
-                  (when-let ((layer-props-list (tp-group-props layer-name t)))
-                    (tp--build-layer-props layer-props-list))))))))
-        (if layer-props
-            ;; Return all property keys from the layer plus tp-name and the layer itself
-            (let ((keys (cl-loop for (key _val) on layer-props by #'cddr
-                                 collect key)))
-              (unless (memq 'tp-name keys)
-                (push 'tp-name keys))
-              (unless (memq layer-name keys)
-                (push layer-name keys))
-              keys)
-          ;; Layer name doesn't match tp-name and layer property doesn't exist
-          ;; Just remove the literal symbol
-          (list layer-name)))
-    ;; Not a layer name, just return the symbol itself
-    (list layer-name)))
-
-(defun tp--expand-props-to-remove (props-to-remove str start)
-  "Expand PROPS-TO-REMOVE list, expanding any layer names to their property keys.
-STR and START are used to determine context for parameterized layers."
-  (let ((result nil))
-    (dolist (prop props-to-remove)
-      (dolist (expanded (tp--expand-layer-to-props-list prop str start))
-        (unless (memq expanded result)
-          (push expanded result))))
-    (nreverse result)))
-
 (defun tp--get-layer-face-contribution (layer-name layer-prop-value)
   "Get the face contribution from LAYER-NAME.
 LAYER-PROP-VALUE is the value of the layer property (the argument passed to it).