added typeaheead and introspetion

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+# Phase 66 — Advanced Data Comparison (bounded preview)
+
+The Schemas navigator now provides **Compare Table Data…** on each database.
+Select another database on the same connection and a shared base table, then click Compare.
+
+The comparison is **read-only**. It compares exact returned row values, including duplicates,
+using counts of canonical JSON-encoded row arrays. Both databases must have matching column
+names and order in their introspection snapshots. Views are excluded.
+
+## Important limitations
+
+- A maximum of **500 rows per database** are compared. An extra row is retrieved to detect truncation.
+- Without a deterministic ordering, MySQL may return different subsets on repeated queries.
+- No primary-key alignment or update detection is implemented in this phase; changed records
+  appear as removed/added row values.
+- The native MySQL protocol currently represents result cells as strings, so SQL NULL and
+  a literal string may not be distinguishable. Do not use this comparison as a data-integrity audit.
+- For large datasets, Phase 67 should implement paginated, key-aware comparison with safe
+  conflict handling before any data synchronisation is offered.
+
+This phase does not modify database records or create synchronization SQL.