ui: P2 polish checklist (trees, motion, chrome)

[ZhuchkaTriplesix]

Parent

Part of epic #490. Lower-priority polish from the UI review — pick items opportunistically.

Checklist

Trees

• Unify leaf icon colors (PG primary tint vs MySQL/SQLite muted)
• Schema indent 12 → shared 16 (or documented scale)
• TreeLoadError presentation consistent (icon/title); SDUI expand errors use it
• Semantics on expand rows (button + expanded)
• Leaf icons for materialized views / sequences where group≠leaf
• Foreign-data icon metaphor (stop reusing publicSchema)

Motion

• QueryaCrossFadeStack: enter/exit curves + index clamp (parity with SwitchingBody)
• QueryaStagger step scaled under Reduced
• Broader QueryaHoverSurface adoption or document card-only scope

Chrome

• Empty hero: avoid Quick start flash before recent loads
• Update dialog phase body cross-fade
• SDUI selects → QueryaDropdown (or shared control)
• Shared tooltip waitDuration constant
• Dialog cards as Material(color: popover) to prevent future ListTile asserts

Non-goals

Anything that belongs in P0/P1 children of #490.

Notes

Mechanical batch shipped in PR for this issue. Remaining unchecked items deferred to a follow-up.

[ZhuchkaTriplesix]

Shipped on dev via #515. Leftovers tracked in #514 (also shipped).