feat: add runtime context awareness — system.info tool + date/time in system prompt

- assembleSystemPrompt() now injects '# Runtime Context' with current date/time
- New system.info tool: date, time, hostname, platform, arch, uptime, memory, Node.js version
- Tool available in all profiles (minimal/messaging/coding/full)
- 983 tests passing (+7 new)

src/prompt/template.ts

@@ -63,10 +63,27 @@ export function assembleSystemPrompt(config: PromptTemplateConfig): PromptTempla
     }
   }
 
-  // Fallback if nothing was loaded
-  if (sections.length === 0) {
+  // Inject current date/time as runtime context
+  const now = new Date();
+  const dateStr = now.toLocaleDateString('en-US', {
+    weekday: 'long',
+    year: 'numeric',
+    month: 'long',
+    day: 'numeric',
+  });
+  const timeStr = now.toLocaleTimeString('en-US', {
+    hour: '2-digit',
+    minute: '2-digit',
+    timeZoneName: 'short',
+    hour12: false,
+  });
+  const runtimeContext = `# Runtime Context\n\nCurrent date: ${dateStr}\nCurrent time: ${timeStr}`;
+  sections.push(runtimeContext);
+
+  // Fallback if only the runtime context was loaded (no actual prompt files)
+  if (sections.length === 1) {
     return {
-      prompt: 'You are Flynn, a helpful personal AI assistant. Be direct, concise, and helpful. Use markdown when it improves readability.',
+      prompt: `You are Flynn, a helpful personal AI assistant. Be direct, concise, and helpful. Use markdown when it improves readability.\n\n${runtimeContext}`,
       loadedFiles: [],
     };
   }