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>

README.md

@@ -19,6 +19,7 @@ claude-foundations/
     post-edit-lint.sh      # PostToolUse: auto-format/lint on Edit/Write
     pre-commit-lint.sh     # Git pre-commit: lint staged files
     pre-compact-backup.sh  # PreCompact: backup transcript before compaction
+    require-plan-file.sh   # PreToolUse/ExitPlanMode: enforce *-PLAN.md exists before leaving plan mode
   scripts/
     install-hooks.sh       # Symlink hooks into ~/.claude/hooks/
     setup-formatters.sh    # Set up formatters for a project