feat(backend/kernel): wire TSparkParameter through to kernel bind_param

[vikrantpuppala]

Summary

Lifts the NotSupportedError the kernel backend currently raises for parametrized queries. The kernel-side PyO3 binding (Statement.bind_param) shipped in databricks-sql-kernel#18; this PR wires the connector's TSparkParameter shape through to it.

Before: cursor.execute("SELECT ?", [IntegerParameter(42)]) on use_kernel=True raised NotSupportedError. After: positional parameter binding works end-to-end.

What it does

bind_tspark_params(kernel_stmt, parameters) in type_mapping.py forwards each TSparkParameter to the kernel as (ordinal, value.stringValue, type):

• ordinal is the 1-based position in the parameters list (matches kernel's SEA-wire convention).
• value.stringValue is the connector's already-string-encoded value (or None for SQL NULL).
• type is the SQL type name the connector produces ("INT", "DECIMAL(10,2)", etc.).

The connector's ordinal: bool flag is checked only to reject named bindings — kernel v0 doesn't accept named bindings on the SEA wire, so we surface that at the connector layer with a pointed NotSupportedError rather than letting the server reject.

What's supported

Every type the connector's native parameter classes emit:

• BOOLEAN, TINYINT / SMALLINT / INT / BIGINT, FLOAT / DOUBLE
• STRING, DATE, TIMESTAMP / TIMESTAMP_NTZ, INTERVAL
• DECIMAL(p,s) (precision/scale carried in the SQL type string; kernel parses them)
• VOID / Python None

What's not supported (known gaps, raises NotSupportedError)

• Named bindings (cursor.execute(":foo = ?", [param_named("foo", ...)])) — kernel v0 SEA wire is positional-only.
• Compound types (ARRAY / MAP / STRUCT) — kernel parser rejects; surfaces as KernelError(InvalidArgument).
• BINARY — SEA wire limitation kernel-side; documented workaround is hex-encode + unhex(?) in SQL.

Test plan

• 6 new unit tests in tests/unit/test_kernel_type_mapping.py for bind_tspark_params — positional forwarding, None / VOID, named-binding rejection, missing-type defaulting, empty list.
• Replaced test_execute_command_rejects_parameters (which previously asserted the NotSupportedError) with test_execute_command_forwards_parameters_to_bind_param: stubs the kernel statement, asserts bind_param is called once per TSparkParameter in order with 1-based ordinals, and execute() fires after binding.
• Full kernel unit suite: 106/106 pass (up from 100 on main).
• 3 new live e2e tests in tests/e2e/test_kernel_backend.py against dogfood:
  • Mixed-type round-trip (IntegerParameter, StringParameter, BooleanParameter)
  • None parameter
  • DECIMAL parameter (precision/scale flows through the SQL type string)
• Full kernel e2e suite: 14/14 pass against dogfood (locally with the kernel wheel built from databricks-sql-kernel main).

This pull request and its description were written by Isaac.