Fix: REMOVE staging operation no longer requires staging_allowed_local_path (#726)

[vikrantpuppala]

Summary

Fixes #726.

A REMOVE staging operation deletes a remote resource and never touches the local filesystem, yet Cursor._handle_staging_operation raised:

You must provide at least one staging_allowed_local_path when initialising a connection to perform ingestion commands

before dispatching to any handler when staging_allowed_local_path was None. This forced callers to pass a dummy path (e.g. "/") just to run a REMOVE, even though the value is never used for that operation — the reporter observed they could PUT via __input_stream__ without a path, but REMOVE still demanded one.

Root cause

In src/databricks/sql/client.py, _handle_staging_operation validated staging_allowed_local_path for every non-streaming operation before dispatch. The REMOVE branch then explicitly popped local_file because "Local file isn't needed to remove a remote resource" — confirming the requirement was spurious for REMOVE.

Fix

Handle REMOVE early, right after the existing __input_stream__ PUT bypass and before the staging_allowed_local_path validation block. GET and local-file PUT continue to require staging_allowed_local_path.

Test plan

Added tests/unit/test_staging_remove.py:

• test_remove_without_staging_allowed_local_path — the repro: REMOVE with staging_allowed_local_path=None now dispatches to _handle_staging_remove (no local_file forwarded) instead of raising. Fails before the fix, passes after.
• test_remove_with_staging_allowed_local_path — REMOVE still works when a path is provided.
• test_get_still_requires_staging_allowed_local_path — regression guard: GET with None still raises the original error.
• test_unsupported_operation_still_errors — unknown operations still raise.

Verification:

• poetry run python -m pytest tests/unit/test_staging_remove.py tests/unit/test_streaming_put.py — 8 passed
• poetry run python -m pytest tests/unit/test_client.py — 128 passed, 2 skipped
• Full unit suite (-m "not realkernel") — 869 passed, 4 skipped
• poetry run black — no changes needed

Added a CHANGELOG entry under a new Unreleased section.

Closes #726