[Docs] README: refresh the hero screenshot for the Tempered theme

[vedanshujain]

Summary

The committed README hero still showed the pre-theme storefront — default blue link
styling, bordered cards. This replaces it with the current Tempered design and updates the
alt text and caption to match.

New shot: the home page's display headline and tagline beside the inventory tape, with live
SKU / price / stock rows served by the commerce service. 1280×600, light theme, taken from
the deployed reference site.

Framing disclosure

This is the home page, whereas the old image used the product grid. That is a
deliberate change, not a convenience.

The grid renders each product's description, and the seeded descriptions are not something
we want as the project's first impression:

• one markets an availability guarantee we have explicitly decided not to claim;
• another explains our own CMS/commerce-service internals to shoppers.

Both are already scheduled to be rewritten in the storefront copy pass. The home page shows
the theme's character — type scale, inventory tape, mono numerals — without carrying that
copy into the README. When the copy pass lands, the grid is a fair candidate again.

Worth noting the old image had the same problem: that copy is visible in the hero on
main today. This PR removes it from the README as a side effect.

Alt text / caption

Both were describing the old image and are now inaccurate, so both changed:

• alt: no longer "a product listing … title, description, and price" — the new image is a
  headline plus a SKU/price/stock table.
• caption: dropped "running locally". The screenshot is from the deployed reference site;
  the caption now says the quick start gives you the same thing locally, which is the claim
  that is actually true.

Verification

• Image renders in the README preview; link path ./docs/storefront.png unchanged.
• No code touched — docs and one binary asset only.
• 47.6 KB → 52.9 KB.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HoB4yKtw1hgN5sEvDfupdt

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