[dominikpeter]

Moves exception construction into Rust (src/errors.rs).

• SQLSTATE to class table, the 1222 / 2628 / 8114 promotions and the driver_error / ddbc_error / sqlstate / native_error attributes are built in Rust; classes are imported once from arrowsql.exceptions. The "Raising exception" / "Unknown SQLSTATE" / "Connection error" log lines still go through the Python logger.
• New DDBCRaiseFor(handle_type, handle, ret) replaces the DDBCSQLCheckError + regex round trip. helpers.check_error calls it, and falls back to the Python path when a test replaced DDBCSQLCheckError / DDBCSQLGetAllDiagRecords.
• Native Connection and getinfo raise typed exceptions. _raise_connection_error stays as a shim for mocks that raise RuntimeError("SQLSTATE:..."). Connection close/rollback sites catch (RuntimeError, Error).
• Native close() with an open transaction (25000) stays a RuntimeError: upstream's test_failed_native_disconnect_preserves_child_statement matches on it.
• exceptions.sqlstate_to_exception / raise_exception are thin shims; the 140-line Python table is gone.
• async hub uses the same builder.

Error path (SELECT * FROM no_such_table, release build): median 184.5us before, 176.5us after; 10k failing executes 1.90s vs 2.02s best of 3. Within noise, the round trip dominates.

Tests: common_issues/port/mock pass; upstream baseline 0 missing before the merge of main.

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