feat(proactive): default to the four core skills (core | all | off); docs, prompt and tests (GSTA-99)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

scripts/question-registry.ts

@@ -548,8 +548,8 @@ export const QUESTIONS = {
     skill: 'preamble',
     category: 'approval',
     door_type: 'two-way',
-    options: ['on', 'off'],
-    description: "Let gstack proactively suggest skills based on conversation context?",
+    options: ['core', 'all', 'off'],
+    description: "Let gstack proactively suggest skills based on conversation context? core (the four core skills, default) / all / off",
   },
   'preamble-routing-injection': {
     id: 'preamble-routing-injection',

scripts/resolvers/preamble/generate-upgrade-check.ts

@@ -8,7 +8,7 @@ import type { TemplateContext } from '../types';
  * the fence prose scopes and the model follows.
  */
 export function generateUpgradeCheck(ctx: TemplateContext): string {
-  return `If \`PROACTIVE\` is \`false\`, do not auto-invoke or suggest skills, including by asking whether to run one. Only run skills the user explicitly invokes.
+  return `If \`PROACTIVE\` is \`false\` or \`off\`, suggest no skill, even by asking; if \`core\` (default), only /office-hours, /review, /qa and /ship; \`all\` or \`true\`: any.
 
-If \`SKILL_PREFIX\` is \`"true"\`, suggest/invoke \`/gstack-*\` names. Disk paths stay \`${ctx.paths.skillRoot}/[skill-name]/SKILL.md\`.`;
+If \`SKILL_PREFIX\` is \`true\`, suggest \`/gstack-*\` names; disk paths stay \`${ctx.paths.skillRoot}/[skill-name]/SKILL.md\`.`;
 }