DoltLite 0.51.6

Added nonlocal tables for sharing data across branches and dolt_dump for SQL and SQLite exports.

• Added dolt_nonlocal_tables with cross-branch transactions, foreign-key support, and dolt_commit_all() to commit participating branches together.
• Added dolt_dump and embedded C APIs to export working, staged, or committed snapshots as SQL or ordinary SQLite databases.
• Improved merge, reset, conflict resolution, branch deletion, and concurrent-reader correctness.
• Updated SQLite upstream with query-planner, FTS5, and vector-index fixes.

Benchmark / SQL workload summary

In-memory

Operation	SQLite median total	DoltLite median total	Ratio
Reads	8.81s	10.28s	1.2×
Writes	1.77s	3.12s	1.8×

File-backed

Operation	SQLite median total	DoltLite median total	Ratio
Reads	9.16s	10.34s	1.1×
Writes	3.33s	4.02s	1.2×
Autocommit writes	841.58ms	2.54s	3.0×

Full nightly results: performance-report.md.