Implement sprints 166-168 production code generation gates and loop

sprint166_plan.md

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+# Sprint 166 Plan: `whetstone_generate_code` for Production Class/Module Output
+
+## Context
+
+Current A/B rerun (2026-02-26) confirms:
+- `whetstone_generate_code` still returns a single-function `printf` stub for
+  class-level specs.
+- `whetstone_run_pipeline` now emits class structure, but still uses placeholder
+  typing and incomplete bodies for production targets.
+
+This sprint upgrades `whetstone_generate_code` from function-stub behavior to a
+deterministic class/module generator suitable for real implementation tasks.
+
+---
+
+## Goals
+
+1. Replace `printf` fallback path for class/module specs
+2. Emit complete class/data-model structure with concrete typed fields/methods
+3. Support PriorityQueue-class pattern end-to-end in generated C++
+4. Return explicit generation quality metadata (not just code text)
+
+---
+
+## Steps
+
+### Step 1874: Spec classifier for function/class/module intent (10 tests)
+
+Add robust intent parsing for `whetstone_generate_code`:
+- identify data model vs service class vs utility function
+- detect multi-method class requests
+- route to class/module builder instead of function stub path
+
+Tests (10): function-only routing, class routing, module routing, mixed intent,
+false-positive rejection, deterministic classification, empty-spec handling,
+high-entropy prompt handling, fallback reason correctness, API compatibility.
+
+### Step 1875: C++ class/data-model emitter with concrete typing (12 tests)
+
+Implement structured C++ emitter for:
+- fields (`std::string`, `int`, `bool`, `double`, vectors/maps where detected)
+- constructors and method signatures with concrete types
+- includes + pragma once + namespace handling
+
+Tests (12): typed field emission, constructor emission, method signature typing,
+include minimization, namespace stability, header parseability, no `auto` in
+public API for inferred primitives, deterministic member ordering, no raw stub
+fallback, unknown-type diagnostic, compatibility with existing `schema_to_cpp`,
+regression on function-only generation.
+
+### Step 1876: PriorityQueue pattern builder (10 tests)
+
+Add first-class support for queue patterns:
+- internal heap storage type
+- enqueue/dequeue/peek/size/empty bodies
+- ordering by priority
+
+Tests (10): method presence, max-heap behavior shape, empty-queue guard paths,
+return type correctness, const-correctness for observers, compile success of
+generated snippet, deterministic output, no placeholder body markers, no `printf`
+fallback, class+data model co-generation.
+
+### Step 1877: Generation quality metadata contract (8 tests)
+
+Extend output payload with machine-checkable fields:
+- `quality.compilable_estimate`
+- `quality.placeholder_count`
+- `quality.todo_count`
+- `quality.fallback_used`
+- `quality.warnings[]`
+
+Tests (8): fields always present, counts accurate, fallback flag accuracy,
+warnings non-empty when uncertain inference used, backward compatibility with
+legacy callers, JSON schema update, deterministic values, docs update.
+
+### Step 1878: Sprint 166 Integration Summary (8 tests)
+
+Add `editor/src/Sprint166IntegrationSummary.h`.
+Record: steps_completed=5 (1874-1878), generate_code_stub_removed_for_classes=true,
+priority_queue_pattern_supported=true, quality_contract_exposed=true, success=true.
+
+Tests (8): constructable summary struct, steps_completed==5, class stub fallback
+removed, PriorityQueue generation path works, metadata present, regression checks
+pass, no API break in tool schema, success==true.
+
+---
+
+## Architecture Gate
+
+- No external dependencies added
+- Keep existing tool name/signature (`whetstone_generate_code`) backward-compatible
+- Class/module specs must never silently degrade to generic `printf` function stubs
+