fix(#2072): thread resolved model into routed-agent spawns (assumptions-analyzer, code-reviewer, code-fixer)

model_overrides / models.<phaseType> were silently inert for gsd-assumptions-analyzer,
gsd-code-reviewer, and gsd-code-fixer on Claude Code: resolveModelInternal honors them,
but the workflows spawned these agents with no model= param, so the resolved value
never reached the Agent tool and the agents inherited the session model — no warning.

Fix — thread each agent's resolved model at every spawn site (the established
plan-phase pattern; the architecture-consistent Claude mechanism, since 13 other
agents already thread their model):
- discuss-phase-assumptions.md: `resolve-model gsd-assumptions-analyzer --raw`
  → ANALYZER_MODEL, threaded.
- code-review.md + code-review-fix.md (re-review): `resolve-model gsd-code-reviewer --raw`
  → REVIEWER_MODEL, threaded.
- code-review-fix.md (both fixer spawns): `resolve-model gsd-code-fixer --raw`
  → FIXER_MODEL, threaded (same silently-inert bug, same file — folded in per review).
- quick.md review step: was reusing `{executor_model}` for gsd-code-reviewer (so the
  reviewer's own override was ignored); init.quick now resolves `reviewer_model`
  (gsd-code-reviewer) and the spawn threads it.

resolve-model --raw returns the bare model string (resolve-execution --raw would
return effort — wrong). The resolver maps these agents to phaseType discuss /
verification / execution, so models.<phaseType> apply too.

Scope: the three agents reachable from the two issue-named workflows + quick.md. The
wider systemic class (other agents in UNTOUCHED workflows with the same pattern) stays
documented on the issue for a maintainer-scoped structural decision (thread-at-source
vs embed-at-install like #2256), not widened here.

Docs: the stale "discuss — reserved, no subagent today" model-profile tables now list
gsd-assumptions-analyzer and the verification row includes gsd-code-reviewer, across
the English docs, the shipped gsd-core/references/model-profiles.md reference, and the
ja-JP / zh-CN / ko-KR / pt-BR locale mirrors.

Tests:
- tests/model-resolver.test.cjs: #2072 acceptance — model_overrides and
  models.discuss/verification/execution resolve for all three agents.
- tests/model-routing-spawn-threading.test.cjs: every spawn of the three agents threads
  a resolved model (fails pre-fix); a header-precise parity guard fails the suite if a
  new un-threaded spawn of any of them regresses.
All 16 golden-install-parity fixtures + the workflow size baseline regenerated for the
changed shipped files (4 workflows + the reference doc); bin/lib is excluded from parity.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.changeset/2072-thread-model-into-routed-agent-spawns.md

@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 2074
+---
+**`model_overrides` and per-phase-type models now actually apply to the assumptions-analyzer, code-reviewer, and code-fixer agents on Claude Code.** Previously `model_overrides["gsd-code-reviewer"]` / `["gsd-assumptions-analyzer"]` / `["gsd-code-fixer"]` (and `models.verification` / `models.discuss` / `models.execution`) were accepted and resolved but silently dropped — the workflows spawned these agents with no model, so they inherited the session model and the configured routing never took effect (no warning). Every spawn now threads its resolved model: `discuss-phase-assumptions`, `code-review`, and `code-review-fix` (both the re-review and the two fixer spawns) resolve it inline, and `quick`'s review step uses the code-reviewer's own resolved model instead of the executor's. The stale "`discuss` — reserved, no subagent" model-profile docs are corrected to list `gsd-assumptions-analyzer`, and the `verification` row now includes `gsd-code-reviewer`. (#2074)