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>

docs/FEATURES.md

@@ -2751,10 +2751,10 @@ Users who run a memory / knowledge-base MCP server (for example, ExoCortex-style
 | Slot | Agents assigned |
 |------|-----------------|
 | `planning` | `gsd-planner`, `gsd-roadmapper`, `gsd-pattern-mapper` |
-| `discuss` | (reserved for future subagent) |
+| `discuss` | `gsd-assumptions-analyzer` |
 | `research` | `gsd-phase-researcher`, `gsd-project-researcher`, `gsd-research-synthesizer`, `gsd-codebase-mapper`, `gsd-ui-researcher` |
 | `execution` | `gsd-executor`, `gsd-debugger`, `gsd-doc-writer` |
-| `verification` | `gsd-verifier`, `gsd-plan-checker`, `gsd-integration-checker`, `gsd-nyquist-auditor`, `gsd-ui-checker`, `gsd-ui-auditor`, `gsd-doc-verifier` |
+| `verification` | `gsd-verifier`, `gsd-plan-checker`, `gsd-integration-checker`, `gsd-nyquist-auditor`, `gsd-ui-checker`, `gsd-ui-auditor`, `gsd-doc-verifier`, `gsd-code-reviewer` |
 | `completion` | (reserved for future subagent) |
 
 **Accepted values:** `"opus"` / `"sonnet"` / `"haiku"` / `"inherit"`