Clear the open minors: lost marking and overrun logging, form teardown guard, line breaks and ERANGE in config, probe strength

The E-1608 source marks every restart as lost and logs each overrun; its form stops touching
siblings after the chooser destroys them; the link skips command id 0, retries a full-buffer
discover send and ignores a zero-length scan read. Session files escape \n and \r; get_int and
get_double reject out-of-range values; the UDPS port spin reports changes; a skipped source panel
says why on stderr. The E-1608 probe now checks the signal names and the reconnect itself.

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

src/layout_store.cpp

@@ -55,12 +55,23 @@ namespace {
 std::string toml_escape(const std::string& s) {
   std::string out = "\"";
   for (char c : s) {
-    if (c == '"' || c == '\\') out.push_back('\\');
-    out.push_back(c);
+    // The file is read line by line, so a raw newline in a value would end the line early.
+    if (c == '\n') {
+      out += "\\n";
+    } else if (c == '\r') {
+      out += "\\r";
+    } else {
+      if (c == '"' || c == '\\') out.push_back('\\');
+      out.push_back(c);
+    }
   }
   return out + "\"";
 }
 
+/// The character an escape `\x` stands for: `\n` and `\r` are the two line breaks, anything else
+/// (the quote, the backslash) stands for itself.
+char unescaped(char c) { return c == 'n' ? '\n' : c == 'r' ? '\r' : c; }
+
 bool unescape(std::string& s) {
   std::string out;
   for (std::size_t i = 0; i < s.size(); ++i) {
@@ -69,8 +80,8 @@ bool unescape(std::string& s) {
       continue;
     }
     if (++i >= s.size()) return false;
-    if (s[i] == '"' || s[i] == '\\') {
-      out.push_back(s[i]);
+    if (s[i] == '"' || s[i] == '\\' || s[i] == 'n' || s[i] == 'r') {
+      out.push_back(unescaped(s[i]));
     } else {
       return false;
     }
@@ -472,8 +483,11 @@ bool load_layout(const std::string& path, LayoutState& out) {
         std::string s = v.substr(1, v.size() - 2);
         std::string out;
         for (std::size_t i = 0; i < s.size(); ++i) {
-          if (s[i] == '\\' && i + 1 < s.size()) ++i;
-          out.push_back(s[i]);
+          if (s[i] == '\\' && i + 1 < s.size()) {
+            out.push_back(unescaped(s[++i]));
+          } else {
+            out.push_back(s[i]);
+          }
         }
         return out;
       }