fix(AppShell): wire up <keyprompt> for multi controltype

[alexwarren]

Summary

• <keyprompt> was silently dropped whenever declared on a "multi" controltype control (useon/selfuseon/give/giveto in CoreEditorObjectUseGive.aslx) — ToControlInfo's "multi" branch never read it, even though ControlInfo.KeyPrompt and the reading pattern for it already exist for stringdictionary/gamebookoptions controls.
• Threads ctrl.GetString("keyprompt") through the "multi" branch alongside the just-added KeyName (fix(AppShell): remove dead <keyname> control hint #2153), and wires it into ScriptDictionaryEditor.svelte's existing keyLabel prop as a tooltip (title attribute) on the add-row input — keyPrompt's longer descriptive sentence (e.g. "Please enter the object name") doesn't fit as placeholder/aria-label text the way keyLabel's short noun ("Object") does.

Stacked on #2153 (base branch set to fix/editor-keyname-hint) since it depends on the KeyName/keyLabel plumbing added there. Part of #2116.

Test plan

• dotnet build --configuration Release / dotnet test --configuration Release — all pass
• npm run check / npm run lint in src/AppShell — clean
• node tests/e2e/find-affected-tests.mjs — ran all 41 flagged scripts; 36 pass, 5 confirmed pre-existing failures unrelated to this change (verified via git stash A/B comparison on the same server)
• Manual verification in-browser: enabled Use/Give on an object, set "Use (other object) on this" to "Handle objects individually" — the add-object dropdown now shows title="Please enter the object name" (resolved [EditorObjectUseGivePleaseenter] text) alongside the existing "Select Object…"/"Add Object" wording from <keyname>

🤖 Generated with Claude Code

[alexwarren]

Closing this rather than rebasing it. Same call as #2153's revert of <keyname>: wiring <keyprompt> up here isn't worth it, for two reasons:

1. It's a hover-only title tooltip — invisible on touch, easy to miss on desktop, the same weak-signal problem fix(AppShell): remove dead <filefiltername> and <preview/> hints #2152 already rejected for <filefiltername>.
2. The text is actively wrong for this control: <keyprompt>'s "Please enter the object name" is an instruction to type a name, but these controls (useon/selfuseon/give/giveto) all set <source>object</source>, so the add-row control is a <select> dropdown of real object names — you pick, you don't type. A tooltip telling you to "enter" a name on a dropdown is worse than no tooltip.

I've removed the dead <keyprompt> tag from the same 4 controls directly on fix/editor-keyname-hint (#2153) instead, matching how the <keyname> tag was handled. <keyprompt> itself stays fully wired and correct for stringdictionary/gamebookoptions controls — only these 4 dead multi-controltype usages are gone.