feat(Flyover): arrange canvas groups horizontally

[kyleve]

Posted by an AI agent on kve's behalf.

Summary

• arrange Flyover groups as a top-aligned horizontal shelf while preserving each group's navigation-depth layout
• fit the initial canvas zoom to the first group and retain Fit All for the complete graph
• point cross-group connectors correctly in either horizontal direction
• refresh Flyover and Where references and add a fitted-all canvas snapshot

Why

Stacking every group vertically made Where's canvas excessively tall. The horizontal shelf reduces its full-content reference height from 10,963 pt to 5,011 pt while keeping screen cards readable at entry.

Review focus

• first-group framing includes the canvas gutters without shrinking to the entire shelf
• backward cross-group transitions attach leading-to-trailing and point their arrows left
• tall fan-outs within an individual group remain intentionally vertical

Testing

• ./swiftformat --lint
• ./test --no-generate FlyoverTests — 39 tests passed
• ./test --snapshots --no-generate --no-build — 42 tests passed
• scoped final Flyover snapshot review — every capture matched byte for byte