Migrate project artifacts to spec-kit format

- Move cross-cutting docs (personas, design system, implementation phases,
  Ideen.md) to .specify/memory/
- Move cross-cutting research and plans to .specify/memory/research/ and
  .specify/memory/plans/
- Extract 5 setup tasks from spec/setup-tasks.md into individual
  specs/001-005/spec.md files with spec-kit template format
- Extract 20 user stories from spec/userstories.md into individual
  specs/006-026/spec.md files with spec-kit template format
- Relocate feature-specific research and plan docs into specs/[feature]/
- Add spec-kit constitution, templates, scripts, and slash commands
- Slim down CLAUDE.md to Claude-Code-specific config, delegate principles
  to .specify/memory/constitution.md
- Update ralph.sh with stream-json output and per-iteration logging
- Delete old spec/ and docs/agents/ directories
- Gitignore Ralph iteration JSONL logs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.specify/templates/agent-file-template.md

@@ -0,0 +1,28 @@
+# [PROJECT NAME] Development Guidelines
+
+Auto-generated from all feature plans. Last updated: [DATE]
+
+## Active Technologies
+
+[EXTRACTED FROM ALL PLAN.MD FILES]
+
+## Project Structure
+
+```text
+[ACTUAL STRUCTURE FROM PLANS]
+```
+
+## Commands
+
+[ONLY COMMANDS FOR ACTIVE TECHNOLOGIES]
+
+## Code Style
+
+[LANGUAGE-SPECIFIC, ONLY FOR LANGUAGES IN USE]
+
+## Recent Changes
+
+[LAST 3 FEATURES AND WHAT THEY ADDED]
+
+<!-- MANUAL ADDITIONS START -->
+<!-- MANUAL ADDITIONS END -->