Refresh README with Cotabby brand banner

[FuJacob]

Summary

Replace the README's separate logo, title, and tagline with one full-width Cotabby brand banner. The new artwork uses the production cat mark and OpenRunde type from the landing project, with a white atmospheric background, soft blue bubbles, and a faded oversized wordmark.

Validation

• Rendered the HTML composition through headless Chrome at 3200×1000.
• Inspected the full-resolution PNG after rendering; logo, [beta] label, tagline, soft shadows, and background details render cleanly without clipping or raster artifacts.
• identify .github/assets/readme/cotabby-banner.png — confirmed a 3200×1000 8-bit sRGB PNG.
• git diff --check — exit 0.

Linked issues

None.

Risk / rollout notes

README-only presentation change. Existing landing, download, and support buttons remain directly below the banner, and the banner continues linking to cotabby.app.

Greptile Summary

This PR refreshes the README header with a Cotabby brand banner. The main changes are:

• A new banner PNG under .github/assets/readme/.
• The README logo image now points to the banner.
• The separate centered title and tagline were removed.

Confidence Score: 5/5

This looks safe to merge after small README presentation cleanups.

• The changes are limited to README markup and a static image asset.
• No application runtime, build, release, or security-sensitive code changed.
• The remaining issues are about README semantics and image layout behavior.

README.md

Important Files Changed

Filename	Overview
README.md	Updates the README header to use the new banner and removes the separate text title/tagline.
.github/assets/readme/cotabby-banner.png	Adds the static banner image referenced by the README.

_{Reviews (1): Last reviewed commit: "Refresh README branding with Cotabby ban..." | Re-trigger Greptile}

Greptile also left 2 inline comments on this PR.

[greptile-apps]

Missing Document Heading

This banner replaces the only <h1> in the README, so the rendered README body now starts with an image and then jumps to ## What It Does. Raw markdown consumers, generated docs, and assistive-tech heading navigation can no longer find the project title as a semantic heading.

[greptile-apps]

Banner Lacks Reserved Height

The new 1600px banner does not include a height, so browsers cannot reserve its aspect ratio before the image loads. On slower connections, the README content can shift after the larger PNG finishes loading.

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