fix(#3602): bind model resolution for every workflow subagent spawn (#3670)

* test(#3602): guard every spawned gsd-* subagent has a model resolution

* fix(#3602): bind model resolution for every workflow subagent spawn

* test(#3602): merge drift-ack entries into their owning fragments

* fix(#3602): address review findings - docs-update verifier binding, ack merge, guard residuals

* chore(#3602): backfill changeset pr number

---------

Co-authored-by: sim <sim@local>

gsd-core/workflows/import.md

@@ -204,13 +204,22 @@ Delegate validation to gsd-plan-checker:
 
 Print: "Delegating to gsd-plan-checker (runs in a subagent — no output until it returns, ~1–5 min; expected, not a freeze)"
 
+```bash
+CHECKER_MODEL=$(gsd_run query resolve-model gsd-plan-checker --raw)
+```
+
 <!-- #2508 runtime-aware-dispatch -->
 
 > **Runtime-aware dispatch (#2508 Phase 4).** GSD workflows dispatch specialized subagents by role. Before dispatching on a built-in-only runtime (kimi-code — three built-ins only), resolve the role to a built-in via `gsd_run query resolve-dispatch-type --requested <role> --raw`. On named-dispatch runtimes (Claude/OpenCode/…) the role is returned unchanged; on kimi-code it maps to `coder`/`explore`/`plan` by role-suffix. The persona rides `${AGENT_SKILLS_<ROLE>}` (Phase 3) regardless. See @gsd-core/references/runtime-aware-dispatch.md.
 
+<!-- #2517 model-omit-on-inherit -->
+
+> **Model omission (#2517).** Omit the `model` parameter entirely when the value it would carry (`CHECKER_MODEL`) is `"inherit"` or empty. An empty value 404s on runtimes without native tier aliases — the default on non-Claude runtimes. Omitting it inherits the orchestrator's model. See @gsd-core/references/model-profile-resolution.md.
+
 ```
 Agent({
   subagent_type: "gsd-plan-checker",
+  model: "{CHECKER_MODEL}",
   prompt: "Validate: ${phase_dir}/{plan}-PLAN.md — check frontmatter completeness, task structure, and GSD conventions. Report any issues."
 })
 ```