[magnusp]

Closes #46.

Part of #54.

What changed

• isSigned now follows xerial's narrow type-name set: true only for NUMERIC, INTEGER, and REAL. BIGINT, SMALLINT, DECIMAL, FLOAT, and DOUBLE report false.
• CAST extraction is case-sensitive, matching xerial: cast(...) is parsed, CAST(...) is not.
• Declared type names are no longer trimmed, and the prefix before the first ( is uppercased exactly as xerial does. A quoted type such as "BIG INT" now reports BIG INT; " NUMERIC " keeps its spaces.
• Malformed precision (DECIMAL(abc)) now propagates NumberFormatException from getPrecision instead of returning 0; getScale still returns 0 because the split has one element.
• An explicitly empty declared type ("") is now treated as present, matching xerial, instead of falling back to runtime sampling.

Contract decision

Parity under #54 is the default, and here parity means copying the xerial 3.53.4.0 quirks deliberately. The case-sensitive CAST pattern, the NumberFormatException on malformed precision, and the narrow isSigned type set are kept on purpose. They are not bugs to "fix" later; changing any of them would break the drop-in contract. Verified against xerial 3.53.4.0 and against sqld/Hrana, which returns the same decltype values for these cases.

Evidence

Tests were added to LibsqlResultSetMetaDataTest first and failed on the pre-fix code (4 failures):

[ERROR] isSignedMatchesXerialNarrowTypeNameSet: [BIGINT] Expecting value to be false but was true
[ERROR] matchesCastOnlyInLowerCase: [uppercase CAST] expected: "INTEGER" but was: "BOOLEAN"
[ERROR] preservesWhitespaceInDeclaredTypeNames: Expecting value to be false but was true
[ERROR] throwsNumberFormatExceptionForMalformedPrecision: Expecting code to raise a throwable

After the fix:

• ./mvnw -pl libsql-jdbc -am test -> BUILD SUCCESS, 127 tests, 0 failures.
• ./mvnw -pl libsql-conformance -am verify -> BUILD SUCCESS, 115 tests, 0 failures, 1 skipped (includes vendored org.sqlite.RSMetaDataTest: 13/13 passing).
• ./mvnw spotless:apply -> BUILD SUCCESS.

Acceptance matrix covered: isSigned for BIGINT, SMALLINT, DECIMAL(10,5), FLOAT, DOUBLE (plus NUMERIC/INTEGER/REAL true cases); upper- and lowercase CAST; quoted type with spaces; DECIMAL(abc).

Deviations

none