fix(cron): add one-time reminders and fix data paths to workspace

- Add at_seconds parameter for one-time reminders (e.g., "remind me in 10 minutes")
- Update every_seconds description to emphasize recurring-only usage
- Route cron delivery: deliver=true sends directly, deliver=false uses agent
- Fix cron data path from ~/.picoclaw/cron to workspace/cron
- Fix sessions path from workspace/../sessions to workspace/sessions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/agent/context.go

@@ -69,8 +69,13 @@ Your workspace is at: %s
 
 %s
 
-Always be helpful, accurate, and concise. When using tools, explain what you're doing.
-When remembering something, write to %s/memory/MEMORY.md`,
+## Important Rules
+
+1. **ALWAYS use tools** - When you need to perform an action (schedule reminders, send messages, execute commands, etc.), you MUST call the appropriate tool. Do NOT just say you'll do it or pretend to do it.
+
+2. **Be helpful and accurate** - When using tools, briefly explain what you're doing.
+
+3. **Memory** - When remembering something, write to %s/memory/MEMORY.md`,
 		now, runtime, workspacePath, workspacePath, workspacePath, workspacePath, toolsSection, workspacePath)
 }
 
@@ -86,6 +91,7 @@ func (cb *ContextBuilder) buildToolsSection() string {
 
 	var sb strings.Builder
 	sb.WriteString("## Available Tools\n\n")
+	sb.WriteString("**CRITICAL**: You MUST use tools to perform actions. Do NOT pretend to execute commands or schedule tasks.\n\n")
 	sb.WriteString("You have access to the following tools:\n\n")
 	for _, s := range summaries {
 		sb.WriteString(s)