[UX] /plugin info <id> panel has dead Install/Remove/Update actions reported as silent success #59

Summary

The detail overlay opened via /plugin info <id> (argument path) renders the same Install / Remove / Update buttons as the browser-opened panel, but registers no event handlers. Activating a button produces an undefined reply that the surface layer treats as silent success. Remove even shows a confirmation dialog first — the user confirms and nothing happens. The identical panel works when opened from the plugin browser, so the same UI behaves differently depending on entry path.

Root cause

• packages/mayfly/src/interaction/plugin-commands.ts:555 builds the overlay with no onEvent handler, unlike the browser path (plugin-commands.ts:429-449).
• With no handler, the endpoint returns an undefined reply without throwing (packages/ui/src/snapshot-events.ts:84-87, :167).
• The interaction surface records an undefined reply as success and closes: packages/mayfly/src/core/ui-interaction-surface.ts:682-686.

Acceptance criteria

• /plugin info <id> wires the same action handlers as the browser path, or renders a read-only detail view with no action buttons.
• An action with no registered handler can never be reported as successful (surface-layer guard or explicit error reply).

Audit reference

docs/audits/2026-09-28-ui-ux-audit-flows-and-localization.md § UX-02 (baseline 27bc188, 2026-09-28)