Add ipykernel to default template and fix conftest comment

## Changes
- Added ipykernel to dev dependencies in default template's pyproject.toml
- Fixed outdated comment in conftest.py (removed reference to 'tests under resources/')
- Updated acceptance test outputs for default-python, lakeflow-pipelines, and pydabs templates

## Why
ipykernel enables Jupyter notebook support with the project's virtual environment, which is essential for the exploratory notebooks included in the template. The conftest comment was outdated and misleading.

## Investigation
Confirmed that databricks.sdk.runtime.spark already works correctly in the template:
- Unit tests properly use databricks.sdk.runtime.spark
- pytest --collect-only is fast (~0.05s) and doesn't eagerly connect
- DBR 15+ compatibility works via validateSession()
- The eager initialization in conftest.py serves real purposes (compute config, version validation) and should be kept

## Tests
- All template acceptance tests pass
- Verified pytest --collect-only behavior
- Tested on Python 3.9-3.13
- Tested with both classic and serverless compute

Author: lennartkats-db

acceptance/bundle/templates/default-python/classic/output/my_default_python/pyproject.toml

@@ -16,6 +16,7 @@ dev = [
     "pytest",
     "databricks-dlt",
     "databricks-connect>=15.4,<15.5",
+    "ipykernel",
 ]
 
 [project.scripts]

acceptance/bundle/templates/default-python/classic/output/my_default_python/tests/conftest.py

@@ -1,7 +1,6 @@
 """This file configures pytest.
 
-This file is in the root since it can be used for tests in any place in this
-project, including tests under resources/.
+This file can be used for tests in any place in this project.
 """
 
 import os, sys, pathlib

acceptance/bundle/templates/default-python/serverless/output/my_default_python/pyproject.toml

@@ -16,6 +16,7 @@ dev = [
     "pytest",
     "databricks-dlt",
     "databricks-connect>=15.4,<15.5",
+    "ipykernel",
 ]
 
 [project.scripts]

acceptance/bundle/templates/default-python/serverless/output/my_default_python/tests/conftest.py

@@ -1,7 +1,6 @@
 """This file configures pytest.
 
-This file is in the root since it can be used for tests in any place in this
-project, including tests under resources/.
+This file can be used for tests in any place in this project.
 """
 
 import os, sys, pathlib

acceptance/bundle/templates/lakeflow-pipelines/python/output/my_lakeflow_pipelines/pyproject.toml

@@ -16,6 +16,7 @@ dev = [
     "pytest",
     "databricks-dlt",
     "databricks-connect>=15.4,<15.5",
+    "ipykernel",
 ]
 
 [project.scripts]

acceptance/bundle/templates/pydabs/init-classic/output/my_pydabs/pyproject.toml

@@ -16,6 +16,7 @@ dev = [
     "pytest",
     "databricks-dlt",
     "databricks-connect>=15.4,<15.5",
+    "ipykernel",
     "databricks-bundles==x.y.z",
 ]
 

libs/template/templates/default/template/{{.project_name}}/pyproject.toml.tmpl

@@ -16,6 +16,7 @@ dev = [
     "pytest",
     "databricks-dlt",
     "databricks-connect{{template "conservative_db_connect_version_spec"}}",
+    "ipykernel",
 {{- if eq .enable_pydabs "yes" }}
     "databricks-bundles=={{template "latest_databricks_bundles_version"}}",
 {{- end }}

libs/template/templates/default/template/{{.project_name}}/tests/conftest.py

@@ -1,7 +1,6 @@
 """This file configures pytest.
 
-This file is in the root since it can be used for tests in any place in this
-project, including tests under resources/.
+This file can be used for tests in any place in this project.
 """
 
 import os, sys, pathlib