[BUG]: Table string cells render as NaN when cells.format is set before initial render, but Plotly.restyle renders correctly

[ym-xie]

Description

When initializing a Plotly go.Table with string cell values such as
"rgb(239, 243, 255)" and setting cells.format=[1] before the first render, the
string values are displayed as NaN.

However, if the same base table is rendered first and the same cells.format value
is then applied dynamically through Plotly.restyle, the table displays the original
string values correctly.

The setting is accepted by plotly.py and stored on the trace object, so this looks
like an initial-render formatting/coercion discrepancy in table traces rather than an
invalid Python-side property assignment.

Screenshots/Video

Steps to reproduce

import io

import plotly
import plotly.graph_objects as go
import plotly.io as pio
from PIL import Image, ImageChops
from playwright.sync_api import sync_playwright


print(f"Plotly version: {plotly.__version__}")

fig = go.Figure(
    go.Table(
        header={"values": ["Color"]},
        cells={"values": [["rgb(239, 243, 255)", "rgb(8, 81, 156)"]]},
    )
)

# Screenshot 1 / plot1.png: set cells.format in Python before the initial render.
fig.data[0].cells.format = [1]
assert fig.data[0].cells.format == (1,)
print("Python-side cells.format:", fig.data[0].cells.format)
html1 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")

# Screenshot 2 / plot2.png: render first, then apply the same value with JS.
fig.data[0].cells.format = None
html2 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")
html2 = html2.replace(
    "</body>",
    """
<script>
window.addEventListener("DOMContentLoaded", () => {
    const plotEl = document.getElementsByClassName("plotly-graph-div")[0];
    setTimeout(() => {
        Plotly.restyle(plotEl, {"cells.format": [1]}, [0]);
    }, 1000);
});
</script>
</body>""",
)

with sync_playwright() as playwright:
    browser = playwright.chromium.launch(
        headless=True,
        args=["--no-sandbox", "--disable-dev-shm-usage", "--disable-gpu"],
    )
    page = browser.new_page(viewport={"width": 1200, "height": 800})

    page.set_content(html1)
    page.wait_for_timeout(1500)
    img1 = page.screenshot(path="plot1.png")

    page.set_content(html2)
    page.wait_for_timeout(2000)
    img2 = page.screenshot(path="plot2.png")

    browser.close()

diff = ImageChops.difference(
    Image.open(io.BytesIO(img1)).convert("RGB"),
    Image.open(io.BytesIO(img2)).convert("RGB"),
)

print("Saved plot1.png and plot2.png")
assert diff.getbbox() is not None, "Reproducer did not reproduce: images are identical."

Notes

Add info here that doesn't fit in the other sections.