Sprint 63: Learned Adapter Hints (Non-Authoritative) — Steps 859-868

Implements the learned adapter hints layer with governance guardrails:
- HintFeatureExtractor: extract features from decision ledgers (step 859)
- HintModelInterface: pair-specific hint query interface (step 860)
- DeterministicFallback: safe fallback when hints unavailable (step 861)
- HintConfidencePacket: confidence bands and escalation logic (step 862)
- HintABHarness: A/B harness to measure hint effectiveness (step 863)
- HintRollbackControl: suppress and lift hint suppression per pair (step 864)
- whetstone_get_adapter_hints MCP tool (step 865)
- whetstone_set_hint_policy MCP tool (step 866)
- HintSafetyGuardrails: non-authoritative enforcement + audit (step 867)
- Sprint63IntegrationSummary (step 868)

All 10 steps passing (94 tests). Governance rule: learned hints may
suggest; deterministic policy decides.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

editor/tests/step864_test.cpp

@@ -0,0 +1,54 @@
+// Step 864: Hint rollback and suppression controls (8 tests)
+#include "graduation/HintRollbackControl.h"
+#include <iostream>
+static int p=0,f=0;
+#define T(n) { std::cout << "  " << #n << "... "; }
+#define P() { std::cout << "PASS\n"; ++p; }
+#define F(m) { std::cout << "FAIL: " << m << "\n"; ++f; }
+#define C(c,m) if(!(c)){F(m);return;}
+
+void t1(){T(suppress_valid);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","py->cpp","bad_hints",true};
+    C(ctrl.suppress(s),"suppress");P();}
+void t2(){T(is_suppressed_after_suppress);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","py->cpp","reason",true};
+    ctrl.suppress(s);
+    C(ctrl.isSuppressed("py->cpp"),"suppressed");P();}
+void t3(){T(not_suppressed_other_pair);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","py->cpp","reason",true};
+    ctrl.suppress(s);
+    C(!ctrl.isSuppressed("rust->go"),"not suppressed");P();}
+void t4(){T(suppress_empty_pair_fails);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","","reason",true};
+    C(!ctrl.suppress(s),"fail");P();}
+void t5(){T(lift_suppression);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","py->cpp","reason",true};
+    ctrl.suppress(s);
+    C(ctrl.lift("py->cpp"),"lift");P();}
+void t6(){T(not_suppressed_after_lift);
+    HintRollbackControl ctrl;
+    HintSuppression s{"S-1","py->cpp","reason",true};
+    ctrl.suppress(s);
+    ctrl.lift("py->cpp");
+    C(!ctrl.isSuppressed("py->cpp"),"not suppressed");P();}
+void t7(){T(active_count);
+    HintRollbackControl ctrl;
+    ctrl.suppress({"S-1","py->cpp","r",true});
+    ctrl.suppress({"S-2","rust->go","r",true});
+    C(ctrl.activeSuppressionsCount()==2,"count");P();}
+void t8(){T(to_json_has_suppression_id);
+    HintSuppression s{"S-1","py->cpp","reason",true};
+    auto j=HintRollbackControl::toJson(s);
+    C(j.contains("suppression_id"),"json");P();}
+
+int main(){
+    std::cout<<"Step 864: Hint rollback and suppression controls\n";
+    t1();t2();t3();t4();t5();t6();t7();t8();
+    std::cout<<"\nResults: "<<p<<"/"<<(p+f)<<" passed\n";
+    return f?1:0;
+}