ci(kernel): install per-tier extras explicitly, not --all-extras

The "Unit Tests + PyArrow" job used --all-extras, which predates the
[kernel] extra. Now that [kernel] exists, --all-extras silently also
installs the kernel wheel — so that tier no longer isolated the
"pyarrow present, kernel absent" configuration and overlapped the new
"Unit Tests + Kernel" job.

- Unit Tests + PyArrow: --extras pyarrow (pyarrow only; no kernel).
- Unit Tests + Kernel:  --extras kernel  (resolves the published
  databricks-sql-kernel wheel via the [kernel] extra — the exact edge
  `pip install databricks-sql-connector[kernel]` uses — which
  transitively brings pyarrow).

Each tier now targets its configuration precisely. The kernel install
path here (published wheel via the extra) is intentionally distinct
from kernel-e2e.yml, which maturin-builds tip-of-tree at KERNEL_REV.

Verified against the proxy: --extras pyarrow installs pyarrow and NOT
the kernel; --extras kernel installs databricks-sql-kernel 0.1.2.

Co-authored-by: Isaac
Signed-off-by: Vikrant Puppala <vikrant.puppala@databricks.com>

Author: vikrantpuppala

.github/workflows/code-quality-checks.yml

@@ -77,7 +77,11 @@ jobs:
         uses: ./.github/actions/setup-poetry
         with:
           python-version: ${{ matrix.python-version }}
-          install-args: "--all-extras"
+          # Install ONLY the pyarrow extra (not --all-extras) so this
+          # tier isolates the "pyarrow present, kernel absent"
+          # configuration. --all-extras would also pull the kernel wheel,
+          # making this job redundant with "Unit Tests + Kernel".
+          install-args: "--extras pyarrow"
           cache-suffix: "pyarrow-${{ matrix.dependency-version }}-"
       - name: Install Python tools for custom versions
         if: matrix.dependency-version != 'default'
@@ -121,9 +125,11 @@ jobs:
         uses: ./.github/actions/setup-poetry
         with:
           python-version: ${{ matrix.python-version }}
-          # --all-extras installs the [kernel] extra, pulling the
-          # published databricks-sql-kernel wheel (+ its pyarrow).
-          install-args: "--all-extras"
+          # Install the kernel extra (pulls the published
+          # databricks-sql-kernel wheel, which transitively brings
+          # pyarrow). Explicit --extras kernel rather than --all-extras
+          # so this tier targets the kernel configuration specifically.
+          install-args: "--extras kernel"
           cache-suffix: "kernel-"
       - name: Show installed versions
         run: |