[AI Setup] Improve .claude/ structure and CLAUDE.md clarity

.claude/docs/mode-system.md

@@ -1,5 +1,7 @@
 # WooPayments Mode System
 
+**Last updated:** 2026-02-13
+
 Reference for how WooPayments determines its operating mode (live, test, dev). Source: `includes/core/class-mode.php`.
 
 ## Mode Hierarchy

.claude/docs/payment-flow.md

@@ -1,5 +1,7 @@
 # Payment Flow — Detailed Reference
 
+**Last updated:** 2026-02-11
+
 This documents the exact call chain for payment operations in WooPayments. Read this when working on payment processing, refunds, or API communication.
 
 ## Payment Intent Creation (Checkout)

.claude/PM_PROMOTIONS.md → .claude/docs/pm-promotions.md

@@ -1,5 +1,7 @@
 # Payment Method (PM) Promotions
 
+**Last updated:** 2025-12-05
+
 ## Overview
 
 PM Promotions display promotional offers for payment methods that merchants haven't yet enabled. The system uses a **flat data structure** where each promotion is a standalone object with a `type` field indicating its display context (spotlight, badge).

.claude/docs/test-patterns.md

@@ -1,5 +1,7 @@
 # Testing Patterns — Reference Guide
 
+**Last updated:** 2026-02-11
+
 Conventions and patterns for writing tests in WooPayments. Read this before writing or modifying tests.
 
 ## PHP Unit Tests

.claude/tmp/.gitignore

@@ -0,0 +1,10 @@
+# Transitory files — code reviews, screenshots, scratch work.
+# Keep directory structure but ignore contents.
+*
+!.gitignore
+!reviews/
+!screenshots/
+reviews/*
+!reviews/.gitkeep
+screenshots/*
+!screenshots/.gitkeep

.gitignore

@@ -11,8 +11,10 @@ project.properties
 *.sublime-workspace
 .sublimelinterrc
 .cursor/
+CLAUDE.local.md
 **/.claude/**/*.local.*
 .claude/local/
+.serena/
 .zed/
 .phpactor.json