Model picker rows: show the short model name beside the provider icon ("Opus 5.5", not "Claude Opus 5.5") #28062

Since #24205, the composer button, sidebar rows, handoff rows and subagent labels show "Opus 5.5" beside the Claude icon. The model picker rows still read "Claude Opus 5.5", "Claude Sonnet 5.5", "Claude Fable 5.1", "Claude Haiku 5.5"... down the whole list, on web and in the mobile picker sheet. That's the same repetition #24205 removed from the button.

In #24205 the picker rows were deliberately kept on full names (comment: "composer labels use the derived short name; picker rows, tooltips and accessibility labels keep full names"), so I'm asking here first instead of sending a PR that reverses that.

Proposal: picker rows use the same derived short name as the composer button, but only where the provider is already visible for that row:

• Web, provider tab selected: the provider rail marks which provider the list belongs to. This includes a locked picker, which still shows the rail with the other providers disabled.
• Web, searching or Favorites: rowsMixProviders is true, so each row already shows its own provider icon and label underneath.
• Mobile picker sheet: rows are grouped under provider headers.

Tooltips, accessibility labels, search matching, and any surface with no provider icon (e.g. the mobile scheduled-task settings row) keep the full name. A custom display name set in settings still wins, same as now.

Before / after on a provider tab:

Claude Opus 5.5        →  Opus 5.5
Claude Sonnet 5.5      →  Sonnet 5.5
Claude Fable 5.1       →  Fable 5.1
Claude Haiku 5.5       →  Haiku 5.5
GPT-5.4 Mini (Codex)   →  5.4 Mini

Shorter rows also put the part that differs between models first, which makes the list quicker to scan.

On the web this is a small change in ModelListRow: it would use getTriggerDisplayModelName(model, driverKind) instead of getDisplayModelName(model). On mobile, the picker sheet rows would use the shortName that ModelOption already carries.

Context: I opened #25739 for this before #24205 landed. It was closed for missing before/after screenshots. If this direction is OK, I'll open a focused PR with screenshots for web and mobile.