fix(auto): persist auto-advance to config and bypass checkpoints

- Write workflow.auto_advance to config.json so auto-mode survives
  context compaction (re-read from disk on every workflow init)
- Auto-approve human-verify and auto-select first option for decision
  checkpoints in both executor and orchestrator
- Pass --auto flag from plan-phase to execute-phase spawn
- Clear auto_advance on milestone complete (Route B)
- Document auto-mode checkpoint behavior in golden rules

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

agents/gsd-executor.md

@@ -168,6 +168,16 @@ Track auto-fix attempts per task. After 3 auto-fix attempts on a single task:
 **In Summary:** Document auth gates as normal flow, not deviations.
 </authentication_gates>
 
+<auto_mode_detection>
+Check if auto mode is active at executor start:
+
+```bash
+AUTO_CFG=$(node ~/.claude/get-shit-done/bin/gsd-tools.cjs config-get workflow.auto_advance 2>/dev/null || echo "false")
+```
+
+Store the result for checkpoint handling below.
+</auto_mode_detection>
+
 <checkpoint_protocol>
 
 **CRITICAL: Automation before verification**
@@ -181,6 +191,14 @@ For full automation-first patterns, server lifecycle, CLI handling:
 
 ---
 
+**Auto-mode checkpoint behavior** (when `AUTO_CFG` is `"true"`):
+
+- **checkpoint:human-verify** → Auto-approve. Log `⚡ Auto-approved: [what-built]`. Continue to next task.
+- **checkpoint:decision** → Auto-select first option (planners front-load the recommended choice). Log `⚡ Auto-selected: [option name]`. Continue to next task.
+- **checkpoint:human-action** → STOP normally. Auth gates cannot be automated — return structured checkpoint message using checkpoint_return_format.
+
+**Standard checkpoint behavior** (when `AUTO_CFG` is not `"true"`):
+
 When encountering `type="checkpoint:*"`: **STOP immediately.** Return structured checkpoint message using checkpoint_return_format.
 
 **checkpoint:human-verify (90%)** — Visual/functional verification after automation.