fix(ui): drop floating divider between hero and how-it-works

[fullstackjam]

Summary

• Remove the border-top hairline on .how-it-works — the only mid-page rule on an otherwise terminal-native layout where the > prompt is the section divider (the community section below already uses prompt-only dividing).
• The asymmetric hero left a large empty band there, so the rule floated in dead space and drew the eye to the void rather than separating content.
• Tighten the section gap to the uniform ~96px rhythm used between every other section so the transition reads as deliberate, not as a missing element.

Test plan

• Verified in the live dev render at 1440px — hero flows into > how it works with balanced spacing, no floating line, no void.
• Change is theme-independent (pure layout; the removed border used a token present in both themes).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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