Add new benchmarks, optimized search, UndoNode pool, and fix horizontal scrolling.

- Added benchmarking for GapBuffer and PieceTable (BufferBench, PerformanceSuite).
- Implemented `OptimizedSearch` using Boyer-Moore (bad character heuristic).
- Introduced `UndoNodePool` for efficient memory management.
- Fixed horizontal scrolling and cursor placement in GUI: ensured cursor visibility and improved accuracy for rendered columns.

test_search_correctness.cc

@@ -0,0 +1,74 @@
+// Verify OptimizedSearch against std::string reference across patterns and sizes
+#include <cassert>
+#include <cstddef>
+#include <random>
+#include <string>
+#include <vector>
+
+#include "OptimizedSearch.h"
+
+
+static std::vector<std::size_t>
+ref_find_all(const std::string &text, const std::string &pat)
+{
+	std::vector<std::size_t> res;
+	if (pat.empty())
+		return res;
+	std::size_t from = 0;
+	while (true) {
+		auto p = text.find(pat, from);
+		if (p == std::string::npos)
+			break;
+		res.push_back(p);
+		from = p + pat.size(); // non-overlapping
+	}
+	return res;
+}
+
+
+static void
+run_case(std::size_t textLen, std::size_t patLen, unsigned seed)
+{
+	std::mt19937 rng(seed);
+	std::uniform_int_distribution<int> dist('a', 'z');
+	std::string text(textLen, '\0');
+	for (auto &ch: text)
+		ch = static_cast<char>(dist(rng));
+	std::string pat(patLen, '\0');
+	for (auto &ch: pat)
+		ch = static_cast<char>(dist(rng));
+
+	// Guarantee at least one match when possible
+	if (textLen >= patLen && patLen > 0) {
+		std::size_t pos = textLen / 3;
+		if (pos + patLen <= text.size())
+			std::copy(pat.begin(), pat.end(), text.begin() + static_cast<long>(pos));
+	}
+
+	OptimizedSearch os;
+	auto got = os.find_all(text, pat, 0);
+	auto ref = ref_find_all(text, pat);
+	assert(got == ref);
+}
+
+
+int
+main()
+{
+	// Edge cases
+	run_case(0, 0, 1);
+	run_case(0, 1, 2);
+	run_case(1, 0, 3);
+	run_case(1, 1, 4);
+
+	// Various sizes
+	for (std::size_t t = 128; t <= 4096; t *= 2) {
+		for (std::size_t p = 1; p <= 64; p *= 2) {
+			run_case(t, p, static_cast<unsigned>(t + p));
+		}
+	}
+	// Larger random
+	run_case(100000, 16, 12345);
+	run_case(250000, 32, 67890);
+	return 0;
+}