fix: address PR #14 review — guard missing context in /model-groups, fix deleteGroup error-after-commit

- model-groups/command.ts: add guard for missing ctx.cwd or ctx.modelRegistry
  before calling createModelGroupsComponent; surface friendly notification
  instead of crashing. Matches refreshModelGroupsState pattern in index.ts.
- model-groups/store.ts deleteGroup(): load opposite-scope config before
  saving the delete so a load failure doesn't throw after the delete is
  already persisted on disk. Follows moveGroup's pre-validation pattern.

Author: grzegorznowak

model-groups/command.ts

@@ -7,6 +7,10 @@ export function registerModelGroupsCommand(pi: ExtensionAPI, state: Agenticoding
 		description: "Manage Model Groups",
 		handler: async (_args, ctx) => {
 			if (!ctx.hasUI) return;
+			if (!ctx.cwd || !ctx.modelRegistry) {
+				ctx.ui.notify("Cannot manage model groups: missing working directory or model registry", "error");
+				return;
+			}
 			await ctx.ui.custom<void>((tui, theme, _keybindings, done) =>
 				createModelGroupsComponent(tui, theme, ctx.modelRegistry, ctx.cwd, done, {
 					initialValidation: state.modelGroups.validation,

model-groups/store.ts

@@ -214,6 +214,10 @@ export function deleteGroup(scope: ModelGroupScope, cwd: string, name: string):
 	const config = loadScopeConfig(scope, cwd);
 	if (!config.groups[name]) throw new Error(`Model group '${name}' does not exist in ${scope} scope`);
 	delete config.groups[name];
+
+	// Load the opposite scope before saving — if this throws, nothing was persisted yet.
+	const other = loadScopeConfig(scope === "global" ? "project" : "global", cwd);
+
 	try {
 		saveModelGroups(scope, cwd, config);
 	} catch (cause) {
@@ -230,7 +234,6 @@ export function deleteGroup(scope: ModelGroupScope, cwd: string, name: string):
 		}
 		throw cause;
 	}
-	const other = loadScopeConfig(scope === "global" ? "project" : "global", cwd);
 	return { otherScopeHasOverride: Boolean(other.groups[name]) };
 }