feat(start-work): update template with --worktree flag documentation

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/features/builtin-commands/templates/start-work.ts

@@ -1,5 +1,14 @@
 export const START_WORK_TEMPLATE = `You are starting a Sisyphus work session.
 
+## ARGUMENTS
+
+- \`/start-work [plan-name] [--worktree <path>]\`
+  - \`plan-name\` (optional): name or partial match of the plan to start
+  - \`--worktree <path>\` (optional): absolute path to an existing git worktree to work in
+    - If specified and valid: hook pre-sets worktree_path in boulder.json
+    - If specified but invalid: you must run \`git worktree add <path> <branch>\` first
+    - If omitted: you MUST choose or create a worktree (see Worktree Setup below)
+
 ## WHAT TO DO
 
 1. **Find available plans**: Search for Prometheus-generated plan files at \`.sisyphus/plans/\`
@@ -15,17 +24,24 @@ export const START_WORK_TEMPLATE = `You are starting a Sisyphus work session.
      - If ONE plan: auto-select it
      - If MULTIPLE plans: show list with timestamps, ask user to select
 
-4. **Create/Update boulder.json**:
+4. **Worktree Setup** (when \`worktree_path\` not already set in boulder.json):
+   1. \`git worktree list --porcelain\` — see available worktrees
+   2. Create: \`git worktree add <absolute-path> <branch-or-HEAD>\`
+   3. Update boulder.json to add \`"worktree_path": "<absolute-path>"\`
+   4. All work happens inside that worktree directory
+
+5. **Create/Update boulder.json**:
    \`\`\`json
    {
      "active_plan": "/absolute/path/to/plan.md",
      "started_at": "ISO_TIMESTAMP",
      "session_ids": ["session_id_1", "session_id_2"],
-     "plan_name": "plan-name"
+     "plan_name": "plan-name",
+     "worktree_path": "/absolute/path/to/git/worktree"
    }
    \`\`\`
 
-5. **Read the plan file** and start executing tasks according to atlas workflow
+6. **Read the plan file** and start executing tasks according to atlas workflow
 
 ## OUTPUT FORMAT
 
@@ -49,6 +65,7 @@ Resuming Work Session
 Active Plan: {plan-name}
 Progress: {completed}/{total} tasks
 Sessions: {count} (appending current session)
+Worktree: {worktree_path}
 
 Reading plan and continuing from last incomplete task...
 \`\`\`
@@ -60,6 +77,7 @@ Starting Work Session
 Plan: {plan-name}
 Session ID: {session_id}
 Started: {timestamp}
+Worktree: {worktree_path}
 
 Reading plan and beginning execution...
 \`\`\`
@@ -68,5 +86,6 @@ Reading plan and beginning execution...
 
 - The session_id is injected by the hook - use it directly
 - Always update boulder.json BEFORE starting work
+- Always set worktree_path in boulder.json before executing any tasks
 - Read the FULL plan file before delegating any tasks
 - Follow atlas delegation protocols (7-section format)`