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>

get-shit-done/workflows/execute-phase.md

@@ -174,7 +174,19 @@ Execute each wave in sequence. Within a wave: parallel if `PARALLELIZATION=true`
 <step name="checkpoint_handling">
 Plans with `autonomous: false` require user interaction.
 
-**Flow:**
+**Auto-mode checkpoint handling:**
+
+Read auto-advance config:
+```bash
+AUTO_CFG=$(node ~/.claude/get-shit-done/bin/gsd-tools.cjs config-get workflow.auto_advance 2>/dev/null || echo "false")
+```
+
+When executor returns a checkpoint AND `AUTO_CFG` is `"true"`:
+- **human-verify** → Auto-spawn continuation agent with `{user_response}` = `"approved"`. Log `⚡ Auto-approved checkpoint`.
+- **decision** → Auto-spawn continuation agent with `{user_response}` = first option from checkpoint details. Log `⚡ Auto-selected: [option]`.
+- **human-action** → Present to user (existing behavior below). Auth gates cannot be automated.
+
+**Standard flow (not auto-mode, or human-action type):**
 
 1. Spawn agent for checkpoint plan
 2. Agent runs until checkpoint task or auth gate → returns structured state