Add Sprints 46-59: governance, porting foundation, and language graduation prep (Steps 689-828)

Sprints 46-58 implement the cross-language porting foundation: language-to-IR
adapters, equivalence checking, gate validation, legacy ingestion, managed/dynamic
families, low-level/logic-actor semantics, debug workflow tooling, AST-native
family tools, Rust/CPP raising tools, system-level orchestration, query family,
and porting gates. Sprint 59 adds the governance layer (policy packs, review
boards, waiver packets, ambiguity triage, decision ledger) with the
whetstone_review_porting_decision MCP tool.

Also includes: sprint plans 46-130, MCP taskitem pipeline scripts,
CLAUDE.md, docs, and full test matrix (steps 689-828).

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

editor/src/debug/BisectCandidateSelector.h

@@ -0,0 +1,26 @@
+#pragma once
+// Step 1481: bisect candidate selector.
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+struct BisectCandidate {
+    std::string proposalId;
+    int index = 0;
+};
+
+class BisectCandidateSelector {
+public:
+    static std::vector<BisectCandidate> ordered(const std::vector<std::string>& proposalIds) {
+        std::vector<BisectCandidate> out;
+        for (size_t i = 0; i < proposalIds.size(); ++i) out.push_back({proposalIds[i], static_cast<int>(i)});
+        std::sort(out.begin(), out.end(), [](const auto& a, const auto& b){ return a.proposalId < b.proposalId; });
+        return out;
+    }
+
+    static BisectCandidate midpoint(const std::vector<BisectCandidate>& orderedCandidates) {
+        if (orderedCandidates.empty()) return {"", -1};
+        return orderedCandidates[orderedCandidates.size() / 2];
+    }
+};