[UX][polish] Interaction nits: digit filters, selection markers, confirmation depth, loading states #75

Summary

Batch of small interaction-consistency defects. Grouped for one polish pass.

UX-22 — Digit conflicts in numbered lists. In a numbered, filterable list, digits are bound to row selection before type-to-filter (packages/mayfly/src/core/ui-key-grammar.ts:278-280 is pushed ahead of the listText search matcher at :300), so a filter query cannot begin with a digit: typing "2024" picks row 2. The / escape hatch exists (:273) but no hint tells the user while the numbered hint (1-9 choose) is displayed. Also, the 1-N hint counts all visible rows including disabled ones (ui-compiler.ts:788, ui-interaction-choice.ts:211-213), but pressing a digit on a disabled row silently does nothing (ui-compiler.ts:2267).

UX-24 — Selection semantics diverge.

• Two marker vocabularies for the same semantics: single-choice lists render ●/space (radio metaphor) and multi-select ●/○ (ui-patterns.ts:274), but expanded form pickers render [x]/[ ] for both single and multi (ui-patterns.ts:373).
• Typing "Other" text silently discards a picked option in single-select questionnaires — questionnaire.ts:56 sets selected: [] whenever custom text is present on a non-multiSelect question; multi-select keeps both, so behavior differs by question type.
• An open Yes/No confirmation vanishes silently when the underlying source changes: ui-interaction-surface.ts:254 drops this.decision with no message.

UX-25 — Confirmation depth. Same-class destructive actions carry three warning levels: rich browse-list Remove (plugin-commands.ts:371) vs bare-string detail-panel Remove (plugin-commands.ts:313) vs bare-string provider Delete (provider-edit.ts:162, though a matching detail translation exists unused at locale.ts:67).

UX-28 — Autocomplete loading gaps. When the skills catalog hasn't settled, the # branch returns null and no dropdown opens — no "loading skills…" row (editor-plus.ts:213-220, skills-catalog.ts:137); the @ path has an empty-result notice (editor-plus.ts:195-197) but no "searching…" row while scans run (pi-tui has no loading-row concept; runAutocompleteRequest cancels on null).

UX-29 — Wizard error on a hidden tab. On a custom endpoint with zero models, Save (provider-add.ts:101-103) fails minSelected: 1 on advertised-models (provider-add.ts:86); the selection-error path focuses but does not activate the hidden tab (ui-interaction-surface.ts:523-526; contrast field errors which do switch tabs at :562-565).

Acceptance criteria

• Filter-first typing works for digits (or the / hatch is hinted); the numbered hint excludes inert digits.
• One marker vocabulary per selection mode; "Other" text never silently discards a selection; confirmation disappearance is explained or prevented.
• Destructive confirmations share one warning convention.
• #/@ autocomplete shows a pending state; wizard errors activate the tab containing the failing control.

Audit reference

docs/audits/2026-09-28-ui-ux-audit-interaction-and-usability.md § UX-22, UX-24, UX-25, UX-28, UX-29 (baseline 27bc188, 2026-09-28)