Add SQL, Erlang, and Forth highlighter implementations and tests for LSP process and transport handling.

- Added highlighters for new languages (SQL, Erlang, Forth) with filetype recognition.
- Updated and reorganized syntax files to maintain consistency and modularity.
- Introduced LSP transport framing unit tests and JSON decoding/dispatch tests.
- Refactored `LspManager`, integrating UTF-16/UTF-8 position conversions and robust diagnostics handling.
- Enhanced server start/restart logic with workspace root detection and logging to improve LSP usability.

test_transport.cc

@@ -0,0 +1,76 @@
+// test_transport.cc - transport framing tests
+#include <cassert>
+#include <cstdio>
+#include <cstring>
+#include <string>
+#include <optional>
+#include <unistd.h>
+
+#include "lsp/JsonRpcTransport.h"
+
+using namespace kte::lsp;
+
+
+static void
+write_all(int fd, const void *bufv, size_t len)
+{
+	const char *buf = static_cast<const char *>(bufv);
+	size_t left     = len;
+	while (left > 0) {
+		ssize_t n = ::write(fd, buf, left);
+		if (n < 0) {
+			if (errno == EINTR)
+				continue;
+			std::perror("write");
+			std::abort();
+		}
+		buf += static_cast<size_t>(n);
+		left -= static_cast<size_t>(n);
+	}
+}
+
+
+int
+main()
+{
+	int p[2];
+	assert(pipe(p) == 0);
+	int readFd  = p[0];
+	int writeFd = p[1];
+
+	JsonRpcTransport t;
+	// We only need inFd for read tests; pass writeFd for completeness
+	t.connect(readFd, writeFd);
+
+	auto sendMsg = [&](const std::string &payload, bool lowerHeader) {
+		std::string header = (lowerHeader ? std::string("content-length: ") : std::string("Content-Length: ")) +
+		                     std::to_string(payload.size()) + "\r\n\r\n";
+		write_all(writeFd, header.data(), header.size());
+		// Send body in two parts to exercise partial reads
+		size_t mid = payload.size() / 2;
+		write_all(writeFd, payload.data(), mid);
+		write_all(writeFd, payload.data() + mid, payload.size() - mid);
+	};
+
+	std::string p1 = "{\"jsonrpc\":\"2.0\",\"id\":1,\"result\":null}";
+	std::string p2 = "{\"jsonrpc\":\"2.0\",\"method\":\"ping\"}";
+	sendMsg(p1, false);
+	sendMsg(p2, true); // case-insensitive header
+
+	auto m1 = t.read();
+	assert(m1.has_value());
+	assert(m1->raw == p1);
+
+	auto m2 = t.read();
+	assert(m2.has_value());
+	assert(m2->raw == p2);
+
+	// Close write end to signal EOF; next read should return nullopt
+	::close(writeFd);
+	auto m3 = t.read();
+	assert(!m3.has_value());
+
+	::close(readFd);
+	std::puts("test_transport: OK");
+	return 0;
+}