fix(client): review fixes for invocation rendering and turn boundaries

The user-turn predicate (opensUserTurn) unifies the three parallel
consumers a new node kind silently missed — produced-files turn reset,
retry liveness, own-words force-scroll — so a skill invocation behaves as
the turn opener it is. The menu marker resolves through ctx.locale.bind
instead of a hand-rolled snapshot lookup; the dead legacy <skill> render
arm goes with the removal cut; command-over-skill name precedence is now
documented at the matchEnter seam; and the emptied replacement catalog
keeps the no-reload sentence, with the never-published residual recorded
in the Agent Note.

packages/skill/tool-skill/src/index.ts

@@ -233,6 +233,7 @@ function renderCatalogUpdate(entries: SkillCatalogSource['entries']): UserMessag
   const availability = entries.length === 0
     ? [
       'No skills are currently available through the `skill` tool. Do not use names from earlier skill catalogs.',
+      'A user may still invoke a skill directly; its <skill_content> block then appears in this conversation. Follow it, and do not call the `skill` tool for it.',
     ]
     : [
       'Use only names in this replacement catalog. If the user names a listed skill, or the task clearly matches its description, call the `skill` tool with the exact name before acting.',