Add midnight README header

[uffejaeger]

Summary

• replace the compact twin-card mark and duplicated hero copy with a full-width midnight-ink SVG header
• use the selected centered-dot Fin and Go pill on a cool blue-black background with subtle brand-color corner circles
• keep the unofficial, community-maintained status visible inside the banner and in accessible alternative text
• remove the now-unused compact mark asset

Impact

The README now opens with one cohesive visual hero while preserving the existing badges, navigation, naming explanation, and documentation content.

Verification

• rendered the SVG at 1200 px with macOS Quick Look and inspected the output
• xmllint --noout docs/assets/intercom-go-header.svg
• git diff --check
• make pre-push with workspace-local Go caches (99.9% coverage, API compatibility, generation check, static analysis, and govulncheck passed)

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Make the banner fill the README width

In GitHub's README rendering, this <img> has no explicit width and the referenced SVG defines only a viewBox, so the browser uses the SVG's default replaced-element size (approximately 300×90 here); GitHub's max-width: 100% styling can shrink images but does not upscale them. Consequently, the intended full-width header appears as a small centered banner unless the image receives an explicit responsive width or the SVG supplies intrinsic dimensions.

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