Merge pull request #909 from lightninglabs/docs-taproot-assets

Update taproot-assets documentation

Author: github-actions[bot]

docs/taproot-assets/debug-handbook/README.md

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+# Debug Handbook
+
+This directory contains debugging guides for common issues encountered in taproot-assets development. Each guide provides pattern recognition techniques, debugging flowcharts, and proven resolution strategies.
+
+## Available Guides
+
+### [PSBT Finalization Failures](./psbt-finalization-failures.md)
+Comprehensive guide for debugging PSBT signing and finalization issues, particularly those involving:
+- BIP32 key derivation mismatches
+- Missing tapscript merkle roots
+- Supply commitment key storage problems
+
+## How to Use This Handbook
+
+1. **Identify symptoms** - Match error messages or behaviors to guide titles
+2. **Follow the flowchart** - Each guide has a decision tree for systematic debugging
+3. **Check common causes** - Most issues follow predictable patterns
+4. **Apply the fix pattern** - Use provided code examples as templates
+5. **Verify resolution** - Run the suggested verification steps
+
+## Contributing New Guides
+
+When you solve a difficult debugging problem, consider adding a guide:
+
+### Guide Template
+
+```markdown
+# [Issue Name] - Debug Handbook
+
+## Quick Identification
+- List symptoms
+- Common error messages
+- Affected components
+
+## Debug Flow Chart
+- Mermaid flowchart showing decision points
+- Clear paths to root causes
+
+## Detailed Debugging Steps
+- Step-by-step investigation process
+- Where to look in code
+- What to check in logs
+
+## Common Pitfalls
+- Things that often trip people up
+- Non-obvious failure modes
+
+## Prevention Strategies
+- How to avoid this issue in the future
+- Best practices
+
+## External References
+- Links to relevant documentation
+- Related specifications or RFCs
+
+## Quick Checklist
+- [ ] Actionable debugging steps
+```
+
+### Good Guide Characteristics
+
+1. **Symptom-focused** - Start with what developers will see
+2. **Systematic approach** - Provide clear debugging methodology
+3. **Code examples** - Show both wrong and right patterns
+4. **Tool commands** - Include exact commands to run
+5. **Cross-references** - Link to relevant code and docs
+6. **Battle-tested** - Based on actual debugging experience
+
+## General Debugging Tips
+
+### Enable Comprehensive Logging
+```bash
+# Maximum verbosity for all components
+export TAPD_DEBUG_LEVEL=debug
+export LND_DEBUG_LEVEL=debug
+export BTCD_DEBUG_LEVEL=debug
+```
+
+### Useful Log Grep Patterns
+```bash
+# Find errors across all logs
+grep -i "error\|fail\|skip\|warn" itest/regtest/*.log
+
+# Track RPC calls
+grep "interceptor.go.*requested" *.log
+
+# Find state transitions
+grep -i "state.*transition\|ProcessEvent" *.log
+
+# Database operations
+grep -i "insert\|update\|upsert" *.log
+```
+
+### Component Interaction Points
+
+Key interfaces where issues often occur:
+- **tapd ↔ lnd**: PSBT signing, wallet operations
+- **tapd ↔ btcd**: Transaction broadcast, block notifications
+- **tapd ↔ universe**: Proof synchronization, supply commits
+- **Database layer**: Key storage, state persistence
+
+### Testing Strategies
+
+1. **Isolate the failure**
+   - Run single test case: `make itest icase=specific_test`
+   - Use unit tests when possible: `go test -v -run TestSpecific`
+
+2. **Simplify the scenario**
+   - Reduce to minimum inputs
+   - Remove unnecessary components
+   - Test with regtest before testnet/mainnet
+
+3. **Add strategic logging**
+   ```go
+   log.Debugf("Key details: family=%d, index=%d, pubkey=%x", 
+       key.Family, key.Index, key.PubKey.SerializeCompressed())
+   ```
+
+4. **Verify assumptions**
+   - Check database state matches expectations
+   - Verify RPC responses contain expected fields
+   - Ensure configuration is correct
+
+## Debugging Tools
+
+### Database Inspection
+```bash
+# SQLite database inspection
+sqlite3 ~/.tapd/data/regtest/tapd.db
+
+# Common queries
+.tables  # List all tables
+.schema supply_commitments  # Show table structure
+SELECT * FROM internal_keys WHERE key_index != 0;  # Find non-zero indices
+```
+
+### PSBT Decoding
+```bash
+# Decode PSBT to human-readable format
+bitcoin-cli decodepsbt "cHNidP8B..."
+
+# Using btcdecode tool
+echo "cHNidP8B..." | btcdecode -psbt
+```
+
+### Transaction Analysis
+```bash
+# Decode raw transaction
+bitcoin-cli decoderawtransaction "0200000001..."
+
+# Get transaction details
+bitcoin-cli getrawtransaction "txid" true
+```
+
+## Common Abbreviations
+
+- **PSBT**: Partially Signed Bitcoin Transaction
+- **BIP32**: Hierarchical Deterministic key derivation
+- **SMT/MSSMT**: Sparse Merkle Tree / Merkle Sum Sparse Merkle Tree
+- **tapd**: Taproot Assets Daemon
+- **lnd**: Lightning Network Daemon
+
+## Learning Resources
+
+- [Bitcoin Optech](https://bitcoinops.org/) - Bitcoin technology explained
+- [BIPs Repository](https://github.com/bitcoin/bips) - Bitcoin Improvement Proposals
+- [Taproot Assets Docs](https://docs.lightning.engineering/the-lightning-network/taproot-assets) - Official documentation
+- [lnd Developer Docs](https://dev.lightning.community/) - Lightning Network development