Add session start bootstrap checklist

SESSION_START.md

@@ -0,0 +1,20 @@
+# Session Start – GPT Execution Bootstrap
+
+Before doing any implementation work in this session:
+
+1. Read `CONSTRAINTS.md`
+2. Open `jester/knowledge-base` and review (as needed):
+   - `ZeroLagHub_Drift_Prevention_Card.md`
+   - `ZeroLagHub_Cross_Project_Tracker.md`
+   - `ZeroLagHub_GPT_Implementation_Handover_Dec2025.md`
+3. Read the latest entry in `SESSION_LOG.md`
+4. Confirm what the goal is for *this* session
+
+## Session Header Template
+Copy/paste this into the top of today’s entry in `SESSION_LOG.md`:
+
+- Date:
+- Goal:
+- Scope:
+- Explicit non-goals:
+- Canonical refs used: