fix: address eleventh round of Copilot PR review feedback

- Validate strategy is a string before set membership check: raise
  PresetValidationError for non-string values (null, list, etc.) and
  normalize to lowercase for case-insensitive matching
- Fix core command name mapping: add speckit.<stem> → <stem>.md fallback
  in resolve(), resolve_with_source(), and collect_all_layers() so core
  command files (named by stem, e.g. plan.md) are found when commands
  use dot notation (e.g. speckit.plan)
- Fix test fixture to use real core layout (plan.md not speckit.plan.md)

Author: mnriem

src/specify_cli/presets.py

@@ -156,6 +156,12 @@ def _validate(self):
 
             # Validate strategy field (optional, defaults to "replace")
             strategy = tmpl.get("strategy", "replace")
+            if not isinstance(strategy, str):
+                raise PresetValidationError(
+                    f"Invalid strategy value: must be a string, "
+                    f"got {type(strategy).__name__}"
+                )
+            strategy = strategy.lower()
             if strategy not in VALID_PRESET_STRATEGIES:
                 raise PresetValidationError(
                     f"Invalid strategy '{strategy}': "
@@ -2037,6 +2043,19 @@ def _get_all_extensions_by_priority(self) -> list[tuple[int, str, dict | None]]:
         all_extensions.sort(key=lambda x: (x[0], x[1]))
         return all_extensions
 
+    @staticmethod
+    def _core_stem(template_name: str) -> Optional[str]:
+        """Extract the stem for core command lookup.
+
+        Commands use dot notation (e.g. ``speckit.specify``), but core
+        command files are named by stem (e.g. ``specify.md``).  Returns
+        the stem if *template_name* follows the ``speckit.<stem>`` pattern,
+        or ``None`` otherwise.
+        """
+        if template_name.startswith("speckit."):
+            return template_name[len("speckit."):]
+        return None
+
     def resolve(
         self,
         template_name: str,
@@ -2111,6 +2130,12 @@ def resolve(
             core = self.templates_dir / "commands" / f"{template_name}.md"
             if core.exists():
                 return core
+            # Fallback: speckit.<stem> → <stem>.md
+            stem = self._core_stem(template_name)
+            if stem:
+                core = self.templates_dir / "commands" / f"{stem}.md"
+                if core.exists():
+                    return core
         elif template_type == "script":
             core = self.templates_dir / "scripts" / f"{template_name}{ext}"
             if core.exists():
@@ -2300,6 +2325,13 @@ def _find_in_subdirs(base_dir: Path) -> Optional[Path]:
             c = self.templates_dir / "commands" / f"{template_name}.md"
             if c.exists():
                 core = c
+            else:
+                # Fallback: speckit.<stem> → <stem>.md
+                stem = self._core_stem(template_name)
+                if stem:
+                    c = self.templates_dir / "commands" / f"{stem}.md"
+                    if c.exists():
+                        core = c
         elif template_type == "script":
             c = self.templates_dir / "scripts" / f"{template_name}{ext}"
             if c.exists():

tests/test_presets.py

@@ -3429,10 +3429,10 @@ def test_resolve_content_override_trumps_composition(self, project_dir, temp_dir
 
     def test_resolve_content_command_type(self, project_dir, temp_dir, valid_pack_data):
         """Test resolve_content with command template type."""
-        # Create core command
+        # Create core command using stem naming (matches real layout: plan.md, not speckit.plan.md)
         commands_dir = project_dir / ".specify" / "templates" / "commands"
         commands_dir.mkdir(parents=True, exist_ok=True)
-        (commands_dir / "speckit.plan.md").write_text("# Core Plan Command\n")
+        (commands_dir / "plan.md").write_text("# Core Plan Command\n")
 
         pack_data = {**valid_pack_data}
         pack_data["preset"] = {**valid_pack_data["preset"], "id": "cmd-append", "name": "CmdAppend"}