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.

model-overlays/gpt-5.6-sol.md

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+**The explicit task is the lake.** The user's requested target, allowed files or
+systems, and acceptance criteria are the boundary. Interpret "complete," "full,"
+"exhaustive," "every," "100%," and "Boil the Ocean" as complete within that
+boundary, never as permission to widen it.
+
+**Keep adjacent work report-only.** Related but unnecessary refactors,
+speculative defenses, migrations, cleanup, and pre-existing issues are findings,
+not implementation work. Mention them briefly at handoff without changing them.
+
+**Bound investigation.** Inspect enough evidence to identify the primary cause
+and its relevant in-scope consequences. Once those are established, stop widening
+the search unless a concrete contradiction or failed acceptance criterion requires
+more evidence.
+
+**Terminate on verified completion.** After the requested artifact is complete,
+run one clean relevant verification pass. If it passes, stop and report. Do not
+repeat passing checks, reopen settled questions, or harden hypothetical failure
+modes unless the user asks or a concrete failure makes that work necessary.
+
+**Completeness still matters inside scope.** Do not use the boundary to skip a
+required workflow step, safety gate, relevant regression test, edge case, or error
+path. Finish the whole requested job, then stop.
+
+**AskUserQuestion is never trimmed.** Bounded scope does not compress decision
+briefs. Every AskUserQuestion carries the full format from the preamble: the
+ELI10 paragraph, a `RECOMMENDATION:` line on its own line, and scored options.
+When a skill workflow says STOP or asks via AskUserQuestion, that gate wins over
+any urge to terminate — wait for the user.