docs: major cleanup and reorganization

- Archive 30 completed session documents to docs/archive/
- Extract learnings to docs/learnings/ (nix-flakes, nostr-sdk, grasp-audit)
- Create CURRENT_STATUS.md as single source of truth
- Create AGENTS.md with documentation guidelines
- Create docs/archive/README.md for archive organization
- Clean root directory: 32 files → 4 files

Root directory now contains only:
- README.md (project overview)
- AGENTS.md (documentation guidelines)
- CURRENT_STATUS.md (current state)
- CLEANUP_SUMMARY.md (cleanup report)

All historical documents preserved in docs/archive/ with proper dating.
All reusable knowledge extracted to docs/learnings/.

Benefits:
- Easy to find current information
- Clear document lifecycle
- No more documentation sprawl
- Learnings are accessible and reusable
- Better onboarding for new developers/agents

File counts:
- Root: 4 (was 32)
- Permanent docs: 7
- Learnings: 3 (new)
- Archive: 32 (new)
- Total: 49 well-organized docs

1 files changed, 0 insertions, 153 deletions

diff --git a/INVESTIGATION_COMPLETE.md b/INVESTIGATION_COMPLETE.md
deleted file mode 100644
index 190a010..0000000
--- a/INVESTIGATION_COMPLETE.md
+++ /dev/null
@@ -1,153 +0,0 @@
-# 🎉 Architecture Investigation Complete
-
-## Summary
-
-I have completed a comprehensive investigation of the GRASP protocol, reference implementation, and Rust ecosystem to design the architecture for **ngit-grasp**.
-
-## Key Finding
-
-✅ **The `git-http-backend` Rust crate is sufficiently flexible to allow inline authorization logic**
-
-We do NOT need Git hooks. We can intercept and validate pushes directly in the HTTP handler before spawning Git.
-
-## Decision
-
-**Use inline authorization** (not pre-receive hooks)
-
-### Why This Is Better
-
-1. **Better UX**: Direct HTTP error responses vs. parsing hook stderr
-2. **Simpler Deployment**: Single Rust binary, no hook management
-3. **Easier Testing**: Pure Rust unit tests, no shell scripts
-4. **Better Performance**: Skip Git spawn for invalid pushes
-5. **Tighter Integration**: Shared state between Git and Nostr components
-
-## Documentation Created
-
-### 📋 For Your Review
-
-1. **[REVIEW_SUMMARY.md](REVIEW_SUMMARY.md)** ⭐ START HERE
-   - Executive summary of investigation
-   - Architecture decision and rationale
-   - Implementation roadmap
-   - Success criteria
-
-### 📚 Architecture Documents
-
-2. **[docs/ARCHITECTURE.md](docs/ARCHITECTURE.md)**
-   - Detailed component design with code examples
-   - Data flow diagrams
-   - Testing strategy
-   - Performance considerations
-   - ~8,000 words of detailed design
-
-3. **[docs/DECISION_SUMMARY.md](docs/DECISION_SUMMARY.md)**
-   - Why inline authorization vs. hooks
-   - Investigation findings
-   - Concerns and mitigations
-
-4. **[docs/COMPARISON.md](docs/COMPARISON.md)**
-   - Side-by-side comparison with ngit-relay
-   - Performance estimates
-   - When to choose each implementation
-
-### 🔧 Technical References
-
-5. **[docs/GIT_PROTOCOL.md](docs/GIT_PROTOCOL.md)**
-   - Git Smart HTTP protocol reference
-   - Pkt-line format explanation
-   - Parsing examples and code snippets
-
-6. **[docs/GETTING_STARTED.md](docs/GETTING_STARTED.md)**
-   - Step-by-step implementation guide
-   - Development workflow
-   - Common issues and solutions
-
-### 📖 Project Files
-
-7. **[README.md](README.md)**
-   - Project overview
-   - Quick start guide
-   - Feature list and roadmap
-
-8. **[docs/README.md](docs/README.md)**
-   - Documentation index
-   - Reading guide for different audiences
-
-9. **[.env.example](.env.example)**
-   - Configuration template
-
-10. **[LICENSE](LICENSE)**
-    - MIT License
-
-## Architecture Overview
-
-```
-┌─────────────────────────────────────────┐
-│      ngit-grasp (Single Binary)         │
-├─────────────────────────────────────────┤
-│                                         │
-│  actix-web HTTP Server                  │
-│         ↓              ↓                │
-│   Git Handlers   Nostr Relay            │
-│         ↓              ↓                │
-│   Inline Auth ← Query State             │
-│         ↓                               │
-│   Spawn Git (if valid)                  │
-│                                         │
-└─────────────────────────────────────────┘
-```
-
-## Technology Stack
-
-- **actix-web**: HTTP server
-- **git-http-backend**: Git protocol (Rust crate)
-- **nostr-relay-builder**: Nostr relay (rust-nostr)
-- **tokio**: Async runtime
-
-## Implementation Estimate
-
-- **~1,400 lines of code** (similar to reference)
-- **4-6 weeks** for GRASP-01 MVP
-- **Well-documented** with extensive examples
-
-## GRASP Compliance
-
-### GRASP-01 (MVP)
-- ✅ Designed and documented
-- ⏭️ Ready to implement
-
-### GRASP-02 (Proactive Sync)
-- ✅ Architecture designed
-- ⏭️ Future phase
-
-### GRASP-05 (Archive)
-- ✅ Architecture designed
-- ⏭️ Future phase
-
-## Recommendation
-
-✅ **Proceed with implementation**
-
-The architecture is:
-- Technically sound
-- Pragmatic and achievable
-- Superior to hook-based approach
-- Well-documented
-- Testable
-- GRASP-compliant
-
-## Next Steps
-
-1. **Review** [REVIEW_SUMMARY.md](REVIEW_SUMMARY.md)
-2. **Review** [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md)
-3. **Approve** or provide feedback on architecture
-4. **Begin implementation** following [docs/GETTING_STARTED.md](docs/GETTING_STARTED.md)
-
-## Questions?
-
-All design decisions are documented with rationale. If you have questions or want to discuss any aspect, the documentation provides detailed context.
-
----
-
-**Ready to build!** 🚀