fix(atlas): enforce checkbox completion before next task

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/agents/atlas/gemini.ts

@@ -309,7 +309,7 @@ task(category="quick", load_skills=[], run_in_background=false, prompt="Task 3..
 - Instruct subagent to append findings (never overwrite)
 
 **Paths**:
-- Plan: \`.sisyphus/plans/{name}.md\` (READ ONLY)
+- Plan: \`.sisyphus\/plans\/{name}.md\` (you may EDIT to mark checkboxes)
 - Notepad: \`.sisyphus/notepads/{name}/\` (READ/APPEND)
 </notepad_protocol>
 
@@ -343,6 +343,7 @@ Subagents CLAIM "done" when:
 - Use lsp_diagnostics, grep, glob
 - Manage todos
 - Coordinate and verify
+- **EDIT \`.sisyphus\/plans\/*.md\` to change \`- [ ]\` to \`- [x]\` after verified task completion**
 
 **YOU DELEGATE (NO EXCEPTIONS):**
 - All code writing/editing
@@ -373,6 +374,20 @@ Subagents CLAIM "done" when:
 - Store and reuse session_id for retries
 - **USE TOOL CALLS for verification — not internal reasoning**
 </critical_rules>
+
+<post_delegation_rule>
+## POST-DELEGATION RULE (MANDATORY)
+
+After EVERY verified task() completion, you MUST:
+
+1. **EDIT the plan checkbox**: Change \`- [ ]\` to \`- [x]\` for the completed task in \`.sisyphus/plans/{plan-name}.md\`
+
+2. **READ the plan to confirm**: Read \`.sisyphus/plans/{plan-name}.md\` and verify the checkbox count changed (fewer \`- [ ]\` remaining)
+
+3. **MUST NOT call a new task()** before completing steps 1 and 2 above
+
+This ensures accurate progress tracking. Skip this and you lose visibility into what remains.
+</post_delegation_rule>
 `
 
 export function getGeminiAtlasPrompt(): string {