Extract TableMetadataResolver from LibsqlResultSetMetaData #205

Goal

Move table metadata lookup out of LibsqlResultSetMetaData. The class currently implements ResultSetMetaData and also queries sqlite_master, pragma_table_info, and pragma_database_list, with attached-schema fallback and a negative cache.

Depends on

#204 for file order, and #195 because the attached-schema branch has no test today.

Pin

LibsqlResultSetMetaDataTest covers aliases, joins, subqueries, RETURNING, views, USING and NATURAL star expansion, generated columns, width mismatches, and non-ASCII names. #195 adds the attached-schema case.

Scope

• Create TableMetadataResolver holding the connection, SQL, column count, lazy resolution, and the LinkedHashMap cache, from LibsqlResultSetMetaData 35 and 397 to 527.
• Move the ColumnInfo and TableInfo records with it.
• Keep tableForColumn(int) as the single entry point for the three callers.

Preserve

• tableContextResolved stays a separate boolean. A resolved null is not an unresolved state.
• The negative cache uses containsKey and put. Do not switch to computeIfAbsent.
• Temp before main fallback, hidden != 1, and COLLATE NOCASE in both queries.
• Lowercased cache keys with the original-case name returned.
• SqlTableReference.resolve receives the column list copy in order.

Acceptance

• TableMetadataResolver.java exists and holds the moved code unchanged.
• LibsqlResultSetMetaData.java is under 300 lines.
• ./mvnw -pl libsql-jdbc -am test green with no assertion edited, including the new attached-schema pin.
• ./mvnw -pl libsql-conformance -am verify green.