Sprint 287: PerTaskLibrarySelector (steps 1963-1967)

Deterministic library dispatch layer. Five new headers:
- LibrarySelection: result struct with avoidedLibraries + justification
- OperationClassifier: wraps taxonomy with ClassificationResult
- PerTaskLibrarySelector: sort by score, pick max, build avoided list
- SelectionJustificationLog: append-only auditable selection log
- Sprint287IntegrationSummary: 8-task spec, all selections verified

25/25 tests passing.

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

editor/tests/step1966_test.cpp

@@ -0,0 +1,99 @@
+// Step 1966: SelectionJustificationLog
+//
+//  t1: append and size
+//  t2: findByDomain returns matching entries only
+//  t3: findByLibrary filters correctly
+//  t4: findByTask returns correct entries
+//  t5: clear resets the log; entries() ordering preserved
+
+#include "SelectionJustificationLog.h"
+#include <iostream>
+
+namespace ws = whetstone;
+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; }
+
+static ws::SelectionJustificationLog makeLog() {
+    ws::SelectionJustificationLog log;
+    log.append({"t1", "serialization.json",  "nlohmann_json", 0.92f,
+                "nlohmann_json scores 0.92 vs protobuf at 0.60", "2026-03-02"});
+    log.append({"t2", "compute.matrix",      "cublas",        0.99f,
+                "cublas scores 0.99 vs numpy at 0.95",          "2026-03-02"});
+    log.append({"t3", "serialization.json",  "serde_json",    0.98f,
+                "serde_json scores 0.98 (only qualified)",      "2026-03-02"});
+    log.append({"t4", "compute.statistics",  "numpy",         0.93f,
+                "numpy scores 0.93 (only qualified library)",   "2026-03-02"});
+    return log;
+}
+
+void t1() {
+    T(append_and_size);
+    ws::SelectionJustificationLog log;
+    C(log.size() == 0, "empty initially");
+    log.append({"t1", "serialization.json", "nlohmann_json", 0.92f, "j", "2026-03-02"});
+    C(log.size() == 1, "size 1 after append");
+    log.append({"t2", "compute.matrix", "cublas", 0.99f, "j", "2026-03-02"});
+    C(log.size() == 2, "size 2 after second append");
+    C(log.entries().size() == 2, "entries() matches size");
+    P();
+}
+
+void t2() {
+    T(findByDomain_filters_correctly);
+    auto log = makeLog();
+    auto json_entries = log.findByDomain("serialization.json");
+    C(json_entries.size() == 2,                  "2 serialization.json entries");
+    C(json_entries[0].taskId == "t1",            "first is t1");
+    C(json_entries[1].taskId == "t3",            "second is t3");
+    auto none = log.findByDomain("network.async");
+    C(none.empty(),                              "no entries for network.async");
+    P();
+}
+
+void t3() {
+    T(findByLibrary_filters_correctly);
+    auto log = makeLog();
+    auto cublas = log.findByLibrary("cublas");
+    C(cublas.size() == 1,              "1 cublas entry");
+    C(cublas[0].operationDomain == "compute.matrix", "correct domain");
+    auto numpy = log.findByLibrary("numpy");
+    C(numpy.size() == 1,               "1 numpy entry");
+    C(numpy[0].capabilityScore == 0.93f, "correct score");
+    P();
+}
+
+void t4() {
+    T(findByTask_returns_correct_entry);
+    auto log = makeLog();
+    auto t2 = log.findByTask("t2");
+    C(t2.size() == 1,                    "1 t2 entry");
+    C(t2[0].selectedLibrary == "cublas", "cublas for t2");
+    auto missing = log.findByTask("t99");
+    C(missing.empty(),                   "no t99 entry");
+    P();
+}
+
+void t5() {
+    T(clear_resets_and_ordering_preserved);
+    auto log = makeLog();
+    C(log.size() == 4, "4 entries before clear");
+    log.clear();
+    C(log.size() == 0,        "empty after clear");
+    C(log.entries().empty(),  "entries() empty after clear");
+    // Re-append and verify ordering preserved
+    log.append({"a", "serialization.json", "nlohmann_json", 0.92f, "j", "2026-03-02"});
+    log.append({"b", "compute.matrix",     "cublas",        0.99f, "j", "2026-03-02"});
+    C(log.entries()[0].taskId == "a", "first entry preserved");
+    C(log.entries()[1].taskId == "b", "second entry preserved");
+    P();
+}
+
+int main() {
+    std::cout << "Step 1966: SelectionJustificationLog\n";
+    t1(); t2(); t3(); t4(); t5();
+    std::cout << "\n" << p << "/" << (p + f) << " passed\n";
+    return f > 0 ? 1 : 0;
+}