feat: gpt-5.6-sol bounded-scope overlay + scope-aware resolvers

The Sol profile pins the explicit task as the lake: adjacent work is
report-only, investigation is bounded, runs terminate on one clean
verification pass, and the AskUserQuestion decision-brief format is never
trimmed. The overlay wrapper grants scope-interpretation precedence while
concrete workflow steps, gates, and skill-mandated re-verification loops
still win. Sol-specific Completeness Principle and first-run intro copy.
New SETUP_COMMAND resolver renders './setup --host <host>' for every
non-claude host so generated upgrade skills reinstall their own host.

scripts/resolvers/preamble/generate-completeness-section.ts

@@ -2,6 +2,13 @@ import type { TemplateContext } from '../types';
 
 export function generateCompletenessSection(ctx?: TemplateContext): string {
   if (ctx?.explainLevel === 'terse') return '';
+  if (ctx?.model === 'gpt-5.6-sol') {
+    return `## Completeness Principle — Boil the Ocean Within Scope
+
+AI makes completeness cheap, so do the complete thing **inside the user's explicit task boundary**. The requested target, allowed files or systems, and acceptance criteria define the lake. Within that lake, cover the relevant tests, edge cases, and error paths. Related but unnecessary refactors, speculative hardening, cleanup, and migrations are separate scope: report them, do not implement them.
+
+When options differ in in-scope coverage, include \`Completeness: X/10\` (10 = all relevant in-scope edge cases, 7 = happy path, 3 = shortcut). When options differ in kind, write: \`Note: options differ in kind, not coverage — no completeness score.\` Do not fabricate scores or expand the lake to raise one.`;
+  }
   return `## Completeness Principle — Boil the Ocean
 
 AI makes completeness cheap, so the complete thing is the goal. Recommend full coverage (tests, edge cases, error paths) — boil the ocean one lake at a time. The only thing out of scope is genuinely unrelated work (rewrites, multi-quarter migrations); flag that as separate scope, never as an excuse for a shortcut.

scripts/resolvers/preamble/generate-lake-intro.ts

@@ -1,6 +1,17 @@
 
+import type { TemplateContext } from '../types';
 
-export function generateLakeIntro(): string {
+export function generateLakeIntro(ctx: TemplateContext): string {
+  if (ctx.model === 'gpt-5.6-sol') {
+    return `If \`LAKE_INTRO\` is \`no\`: say "gstack follows the **Boil the Ocean** principle — do the complete thing within the user's explicit task boundary when AI makes marginal cost near-zero. Do not widen that boundary to adjacent cleanup or speculative hardening. Read more: https://garryslist.org/posts/boil-the-ocean" Offer to open:
+
+\`\`\`bash
+open https://garryslist.org/posts/boil-the-ocean
+touch ~/.gstack/.completeness-intro-seen
+\`\`\`
+
+Only run \`open\` if yes. Always run \`touch\`.`;
+  }
   return `If \`LAKE_INTRO\` is \`no\`: say "gstack follows the **Boil the Ocean** principle — do the complete thing when AI makes marginal cost near-zero. Read more: https://garryslist.org/posts/boil-the-ocean" Offer to open:
 
 \`\`\`bash