feat: update plot sample to 1000 rows

[tswast]

In making a line plot sample with Salem, I noticed that 100 rows loses some important shape information. Most screens are > 1000 pixels wide, so this seems a reasonable default.

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Fixes #<issue_number_goes_here> 🦕

[tswast]

Maybe 500 or something would be better? 640x480 was a very common resolution in the 1990s.

[chelsea-lin]

I investigated how sample size affects the shape of a dataset. My findings (see document: https://docs.google.com/document/d/1KaIF7zX-7seXsb-rohl56jYjhjFdLc-HlNOYfTM1Zfw/edit?tab=t.0) indicate that:

• Samples of size 500 (sampling_n=500) broadly reflect the same shape as a sample of 1000.
• A sample size of 1000 yields a closer approximation to the true underlying distribution.

Maybe we can proceed with a sample size of 1000? Visualize the denser data in the graph for a more informative representation?

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