feat: add Game of Life simulation mechanics

Implement Conway rules with tick timing, pause/resume, single stepping,
speed control, and paused-only cell editing with drag painting. Update
default key bindings for pause/step/speed. Mark verification complete.

config.c

@@ -60,11 +60,14 @@ int config_parse_mods(const char *s, uint32_t *out_mods, char **out_key) {
     while (t) {
         char *tt = trim(t);
         if (*tt) {
+            char *alias = tt;
+            if (strcmp(tt, "+") == 0) alias = "plus";
+            else if (strcmp(tt, "-") == 0) alias = "minus";
             if (n == cap) {
                 cap = cap ? cap * 2 : 4;
                 toks = realloc(toks, cap * sizeof(char *));
             }
-            toks[n++] = strdup(tt);
+            toks[n++] = strdup(alias);
         }
         t = strtok_r(NULL, "+", &save);
     }
@@ -129,6 +132,10 @@ config_t config_defaults(void) {
         {"space", ACTION_ROTATE},
         {"escape", ACTION_CANCEL},
         {"ctrl+q", ACTION_QUIT},
+        {"p", ACTION_PAUSE},
+        {"n", ACTION_STEP},
+        {"+", ACTION_SPEED_UP},
+        {"-", ACTION_SPEED_DOWN},
     };
     int ndef = sizeof(defs) / sizeof(defs[0]);
     for (int i = 0; i < ndef; i++) {
@@ -152,7 +159,11 @@ static const char *default_file_content =
     "\"4\" = \"select:toad\"\n"
     "\"space\" = \"rotate\"\n"
     "\"escape\" = \"cancel\"\n"
-    "\"ctrl+q\" = \"quit\"\n";
+    "\"ctrl+q\" = \"quit\"\n"
+    "\"p\" = \"pause\"\n"
+    "\"n\" = \"step\"\n"
+    "\"+\" = \"speed_up\"\n"
+    "\"-\" = \"speed_down\"\n";
 
 int config_ensure_default_file(const char *path) {
     if (!path) return -1;