Add best practices, hooks, memory files, and scripts from recent sessions

Includes: spec-driven and test-driven development best practices,
reproduce-before-fixing debugging workflow, require-plan-file hook,
find-project-root script, session logs, memory files for decisions/
gotchas/process-lessons, and updates to existing best practice topics.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/find-project-root

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Walk up from CWD to find the highest directory containing CLAUDE.md.
+# Usage:
+#   eval "$(scripts/find-project-root)"   # sets CLAUDE_PROJECT_ROOT
+#   export CLAUDE_PROJECT_ROOT="$(scripts/find-project-root --print)"
+#
+# With --print: outputs just the path (for subshell capture).
+# Without flags: outputs an export statement (for eval).
+
+set -euo pipefail
+
+root=""
+dir="$(pwd)"
+while [[ "$dir" != "/" ]]; do
+    if [[ -f "$dir/CLAUDE.md" ]]; then
+        root="$dir"
+    fi
+    dir="$(dirname "$dir")"
+done
+
+if [[ -z "$root" ]]; then
+    echo "ERROR: No CLAUDE.md found in any parent directory of $(pwd)" >&2
+    exit 1
+fi
+
+if [[ "${1:-}" == "--print" ]]; then
+    echo "$root"
+else
+    echo "export CLAUDE_PROJECT_ROOT=\"$root\""
+fi