scripts: fix create-host flake.nix insertion point

Fix bug where new hosts were added outside of nixosConfigurations block
instead of inside it.

Issues fixed:
1. Pattern was looking for "packages =" but actual text is "packages = forAllSystems"
2. Replacement was putting new entry AFTER closing brace instead of BEFORE
3. testvm01 was at top-level flake output instead of in nixosConfigurations

Changes:
- Update pattern to match "packages = forAllSystems"
- Put new entry BEFORE the closing brace of nixosConfigurations
- Move testvm01 to correct location inside nixosConfigurations block

Result: nix flake show now correctly shows testvm01 as NixOS configuration

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

scripts/create-host/manipulators.py

@@ -50,17 +50,17 @@ def update_flake_nix(config: HostConfig, repo_root: Path, force: bool = False) -
         if count == 0:
             raise ValueError(f"Could not find existing entry for {config.hostname} in flake.nix")
     else:
-        # Insert new entry before closing brace
-        # Pattern: "      };\n      packages ="
-        pattern = r"(      \};)\n(      packages =)"
-        replacement = rf"\g<1>\n{new_entry}\g<2>"
+        # Insert new entry before closing brace of nixosConfigurations
+        # Pattern: "      };\n      packages = forAllSystems"
+        pattern = r"(      \};)\n(      packages = forAllSystems)"
+        replacement = rf"{new_entry}\g<1>\n\g<2>"
 
         new_content, count = re.subn(pattern, replacement, content)
 
         if count == 0:
             raise ValueError(
                 "Could not find insertion point in flake.nix. "
-                "Looking for pattern: '      };\\n      packages ='"
+                "Looking for pattern: '      };\\n      packages = forAllSystems'"
             )
 
     flake_path.write_text(new_content)