feat: add /weigh approach-comparison command to draft welcome

Add /weigh as a draft chip and command for the moment before planning —
when you know what to build but not how. Its hidden prompt investigates
the code, then lays out 2-3 genuinely distinct approaches with trade-offs
(complexity, risk, blast radius, effort) and a clear recommendation,
without writing a plan or code.

Follows the established command pattern: visible + hidden magic prompts
wired into command autocomplete, the submit handler, draft preset chips,
and the Magic Prompts settings page, with i18n across all locales. Adds a
scales-3 icon to the sprite.

packages/ui/src/components/chat/ChatInput.tsx

@@ -101,6 +101,7 @@ type DraftPreset = {
 const DRAFT_PRESETS: readonly DraftPreset[] = [
     { id: 'explore', icon: 'compass-3', labelKey: 'chat.draftPresets.explore.label', promptKey: 'chat.draftPresets.explore.prompt' },
     { id: 'catchup', icon: 'history', labelKey: 'chat.draftPresets.catchup.label', command: '/catch-up' },
+    { id: 'weigh', icon: 'scales-3', labelKey: 'chat.draftPresets.weigh.label', command: '/weigh' },
     { id: 'plan', icon: 'survey', labelKey: 'chat.draftPresets.plan.label', command: '/plan-feature' },
     { id: 'debug', icon: 'bug', labelKey: 'chat.draftPresets.debug.label', command: '/debug' },
     { id: 'review', icon: 'search-eye', labelKey: 'chat.draftPresets.review.label', command: '/workspace-review' },
@@ -1123,7 +1124,7 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
     const availableSkills = useSkillsStore((s) => s.skills);
     const knownSlashNames = React.useMemo(() => {
         const names = new Set<string>([
-            'init', 'review', 'undo', 'redo', 'timeline', 'compact', 'summary', 'workspace-review', 'plan-feature', 'catch-up', 'debug',
+            'init', 'review', 'undo', 'redo', 'timeline', 'compact', 'summary', 'workspace-review', 'plan-feature', 'catch-up', 'debug', 'weigh',
         ]);
         for (const command of availableCommands) names.add(command.name.toLowerCase());
         for (const skill of availableSkills) names.add(skill.name.toLowerCase());
@@ -2017,6 +2018,28 @@ const ChatInputComponent: React.FC<ChatInputProps> = ({ onOpenSettings, scrollTo
                 }
                 return;
             }
+            else if (commandName === 'weigh' && (currentSessionId || newSessionDraftOpen)) {
+                try {
+                    await sessionActions.waitForConnectionOrThrow();
+                    const visibleText = await renderMagicPrompt('session.weigh.visible');
+                    const instructionsText = await renderMagicPrompt('session.weigh.instructions');
+                    await sendMessage(
+                        visibleText,
+                        providerIdToSend,
+                        modelIdToSend,
+                        agentNameToSend,
+                        [],
+                        agentMentionName,
+                        [{ text: instructionsText, synthetic: true }],
+                        variantToSend,
+                        inputMode,
+                    );
+                    scrollToBottom?.();
+                } catch (error) {
+                    toast.error(error instanceof Error ? error.message : t('chat.chatInput.toast.weighFailed'));
+                }
+                return;
+            }
         }
 
         const currentSessionDirectory = currentSessionId

packages/ui/src/components/chat/CommandAutocomplete.tsx

@@ -164,6 +164,10 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
             ? [{ id: 'openchamber:debug', name: 'debug', source: 'openchamber' as const, description: t('chat.commandAutocomplete.command.debugDescription'), isOpenChamber: true }]
             : []
           ),
+          ...(canStartSessionCommand
+            ? [{ id: 'openchamber:weigh', name: 'weigh', source: 'openchamber' as const, description: t('chat.commandAutocomplete.command.weighDescription'), isOpenChamber: true }]
+            : []
+          ),
         ];
         const allCommands = [...builtInCommands, ...customCommands, ...skillCommands];
 
@@ -221,6 +225,10 @@ export const CommandAutocomplete = React.forwardRef<CommandAutocompleteHandle, C
             ? [{ id: 'openchamber:debug', name: 'debug', source: 'openchamber' as const, description: t('chat.commandAutocomplete.command.debugDescription'), isOpenChamber: true }]
             : []
           ),
+          ...(canStartSessionCommand
+            ? [{ id: 'openchamber:weigh', name: 'weigh', source: 'openchamber' as const, description: t('chat.commandAutocomplete.command.weighDescription'), isOpenChamber: true }]
+            : []
+          ),
         ];
 
         const filtered = (searchQuery