[magnusp]

Fixes #208

What

Replaces the positional shaping in getColumns with named records.

• COLUMN_COLUMNS: the 24 Col entries lifted to a static constant beside FOREIGN_KEY_COLUMNS. Values and order unchanged.
• ColumnMetadata (new, package-private): the whole getColumns shape.
  • PragmaRow.fromRow(Row) names the nine pragma_table_xinfo positions once.
  • JdbcRow.toRow() names every one of the 24 JDBC columns.
  • columnShape/ColumnShape moved verbatim from LibsqlDatabaseMetaData, where they had no other caller.
• getColumns now delegates to ColumnMetadata.columns(raw, COLUMN_COLUMNS) and contains no positional values.get(n).

Preserved exactly: IS_AUTOINCREMENT is the primary-key flag and the grammar result; IS_GENERATEDCOLUMN is hidden == 2 || hidden == 3; NULLABLE derives from notnull only; REMARKS stays NULL; the SQL_* and SCOPE_* columns keep their values; NUM_PREC_RADIX stays the literal 10; BUFFER_LENGTH and CHAR_OCTET_LENGTH stay 2_000_000_000. No SQL text touched.

Diff

 .../libsql/jdbc/ColumnMetadata.java           | 177 +++++++++++++++++++++
 .../libsql/jdbc/LibsqlDatabaseMetaData.java   | 159 ++++--------------
 2 files changed, 205 insertions(+), 131 deletions(-)

Line counts: LibsqlDatabaseMetaData.java 949 -> 846 (target under 900); new ColumnMetadata.java 177.

Probe

Set NULLABLE to always columnNullable in JdbcRow.toRow(), then:

LibsqlDatabaseMetaDataTest.getColumnsReportsDeclaredTypesSizesNullabilityAndAutoIncrement:349
expected: 0 but was: 1
Tests run: 54, Failures: 1, Errors: 0

Reverted; the full suite is green afterward.

Lanes

Lane	Result
./mvnw -pl libsql-jdbc -am test	398 tests, 0 failures, 0 errors
./mvnw spotless:check	SUCCESS
./mvnw -pl libsql-conformance -am verify	272 tests, 0 failures, 7 skipped

No test assertion edited, no pom.xml change.