fix(AppShell): wire up <keyname> control hint

[alexwarren]

Summary

• Part of Editor: several v5 .aslx control hints not wired through to AppShell (freetext, min/max/increment, nullable, width, ...) #2116.
• <keyname> was fully dead (4 uses, all in CoreEditorObjectUseGive.aslx on the useon/selfuseon multi controls). A multi control's nested scriptdictionary sub-editor (e.g. "Use (other object) on this" → "Handle objects individually") always showed generic "Add entry key…" / "Select object…" wording, even though these particular keys are specifically object names and the .aslx already declares <keyname>Object</keyname> to say so.
• Threads ctrl.GetString("keyname") through the "multi" branch of ToControlInfo into a new keyLabel prop on ScriptDictionaryEditor.svelte, which swaps in the more specific wording ("Add Object…" / "Select Object…") when set, and falls back to the existing generic text otherwise (both call sites of ScriptDictionaryEditor under a "multi" sub-editor pass it; the unrelated top-level scriptdictionary controltype call site, e.g. AttributesEditor, is untouched since <keyname> never applies there).

Noticed in passing but out of scope: the same useon/selfuseon controls also declare <keyprompt>, which is also dead for "multi" controls specifically (it's already wired for stringdictionary/gamebookoptions, just not multi) - not part of this issue's tracked tag list, so left alone here rather than expanding scope.

Test plan

• dotnet build --configuration Release
• dotnet test --configuration Release (all passing)
• npm run check / npm run lint in src/AppShell (clean)
• node tests/e2e/find-affected-tests.mjs + ran the relevant flagged scripts (verify-appshell-verbs-editor, verify-appshell-attributes-panel-pinned) against a local dev server - all pass.
• Manual check in-browser: enabled an object's Use/Give feature, set "Use (other object) on this" to "Handle objects individually", and confirmed the resulting object picker's aria-label reads "Add Object" and its default option reads "Select Object…" (previously the generic "Add entry key" / "Select object…").

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