Search And Replace: Search Filters: wrong number of selected cells

## Description

"Search Filters" pane of "Search And Replace" widget
shows wrong number of selected cells.

## Reproduce

1. Open Jupyter Notebook.
2. Create a cell.
3. Select both cells with `+`.
4. Actual: 2 cells are selected.
5. Press `+F`.
6. "Search And Replace" widget appears.
7. Click `Show Search Filters`.
8. "Search Filters" pane appears.
9. Expected: `Search in 2 Selected Cells`.
10. Actual: `Search in 1 Selected Cell`.

## Expected behavior

"Search Filters" pane of "Search And Replace" widget
shows wrong number of selected cells:
`Search in 2 Selected Cells`.

## Context

- Operating System and version: Calculate Linux (Gentoo-like).
- Browser and version: Chromium 149.0.7827.200.

- Jupyter Notebook version: 7.6.1.

Troubleshoot Output

which: no jupyter in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/bin:/usr/lib/llvm/22/bin)

$PATH:

	/usr/local/sbin

	/usr/local/bin

	/usr/sbin

	/usr/bin

	/sbin

	/bin

	/opt/bin

	/usr/lib/llvm/22/bin


sys.path:

	/home/sasha/python-venv/bin

	/usr/lib/python313.zip

	/usr/lib/python3.13

	/usr/lib/python3.13/lib-dynload

	/home/sasha/python-venv/lib/python3.13/site-packages

sys.executable:

	/home/sasha/python-venv/bin/python

sys.version:

	3.13.14 (main, Jun 14 2026, 18:09:13) [GCC 15.2.1 20260214]

platform.platform():

	Linux-6.18.33-calculate-x86_64-Intel-R-_Core-TM-_i5-7200U_CPU_@_2.50GHz-with-glibc2.43

pip list:

	Package                   Version

	------------------------- -----------

	anyio                     4.14.2

	argon2-cffi               25.1.0

	argon2-cffi-bindings      25.1.0

	arrow                     1.4.0

	asttokens                 3.0.2

	async-lru                 2.3.0

	attrs                     26.1.0

	babel                     2.18.0

	beautifulsoup4            4.15.0

	bleach                    6.4.0

	certifi                   2026.7.22

	cffi                      2.1.0

	charset-normalizer        3.4.9

	comm                      0.2.3

	debugpy                   1.8.21

	defusedxml                0.7.1

	et_xmlfile                2.0.0

	executing                 2.2.1

	fastjsonschema            2.22.1

	fqdn                      1.5.1

	h11                       0.16.0

	httpcore                  1.0.9

	httpx                     0.28.1

	idna                      3.18

	ipykernel                 7.3.0

	ipython                   9.16.1

	ipython_pygments_lexers   1.1.1

	ipywidgets                8.1.8

	isoduration               20.11.0

	jedi                      0.20.0

	Jinja2                    3.1.6

	json5                     0.15.0

	jsonpointer               3.1.1

	jsonschema                4.26.0

	jsonschema-specifications 2025.9.1

	jupyter                   1.1.1

	jupyter_builder           1.2.1

	jupyter_client            8.9.1

	jupyter-console           6.6.3

	jupyter_core              5.9.1

	jupyter-events            0.12.1

	jupyter-lsp               2.3.1

	jupyter_server            2.20.0

	jupyter_server_terminals  0.5.4

	jupyterlab                4.6.2

	jupyterlab_pygments       0.3.0

	jupyterlab_server         2.28.0

	jupyterlab_widgets        3.0.16

	lark                      1.3.1

	MarkupSafe                3.0.3

	matplotlib-inline         0.2.2

	mistune                   3.3.4

	nbclient                  0.11.0

	nbconvert                 7.17.1

	nbformat                  5.10.4

	nest-asyncio2             1.7.2

	notebook                  7.6.1

	notebook_shim             0.2.4

	numpy                     2.5.1

	openpyxl                  3.1.5

	packaging                 26.2

	pandas                    3.0.3

	pandocfilters             1.5.1

	parso                     0.8.7

	pexpect                   4.9.0

	pip                       26.2

	platformdirs              4.11.0

	prometheus_client         0.26.0

	prompt_toolkit            3.0.53

	psutil                    7.2.2

	ptyprocess                0.7.0

	pure_eval                 0.2.3

	pycparser                 3.0

	Pygments                  2.20.0

	python-dateutil           2.9.0.post0

	python-json-logger        4.1.0

	PyYAML                    6.0.3

	pyzmq                     27.1.0

	referencing               0.37.0

	requests                  2.34.2

	rfc3339-validator         0.1.4

	rfc3986-validator         0.1.1

	rfc3987-syntax            1.1.0

	rpds-py                   2026.6.3

	Send2Trash                2.1.0

	setuptools                83.0.0

	six                       1.17.0

	soupsieve                 2.9.1

	stack-data                0.6.3

	terminado                 0.18.1

	tinycss2                  1.5.1

	tornado                   6.5.7

	traitlets                 5.16.1

	typing_extensions         4.16.0

	tzdata                    2026.3

	uri-template              1.3.0

	urllib3                   2.7.0

	wcwidth                   0.8.2

	webcolors                 25.10.0

	webencodings              0.5.1

	websocket-client          1.9.0

	wheel                     0.47.0

	widgetsnbextension        4.0.15

Command Line Output

Browser Output

Start by reproducing the issue in the Search And Replace widget using the documented two-cell selection steps on Jupyter Notebook 7.6.1. Trace the Search Filters pane's selected-cell count and add regression coverage if the existing test structure identifies a suitable entry point. Done means the pane displays “Search in 2 Selected Cells” for two selected cells.

Written by the indexing model from the issue text.