Constructors and context -> sys

We can register memory we've allocated onto the heap into a ~sys_t~
instance for examination (read: garbage collection) later.  We can
also add items to the symbol table it has internally.

sys.c

@@ -0,0 +1,77 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the Unlicense for details.
+
+ * You may distribute and modify this code under the terms of the Unlicense,
+ * which you should have received a copy of along with this program.  If not,
+ * please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-20
+ * Description: System management
+ */
+
+#include "./base.h"
+
+#include <assert.h>
+#include <malloc.h>
+#include <string.h>
+
+void sys_init(sys_t *sys)
+{
+  sys->memory = NIL;
+  sym_table_init(&sys->symtable);
+}
+
+void sys_register(sys_t *sys, lisp_t *ptr)
+{
+  // Generate an unmanaged cons
+  cons_t *cons = calloc(1, sizeof(*cons));
+  cons->car    = ptr;
+  cons->cdr    = sys->memory;
+  sys->memory  = tag_cons(cons);
+}
+
+void sys_cleanup(sys_t *sys)
+{
+  static_assert(NUM_TAGS == 5);
+
+  sym_table_cleanup(&sys->symtable);
+
+  if (!sys->memory)
+    return;
+
+  // Iterate through each element of memory
+  for (lisp_t *cell = sys->memory, *next = CDR(cell); cell;
+       cell = next, next = CDR(cell))
+  {
+    // Only reason allocated exists is because we had to allocate memory on the
+    // heap for it.  It's therefore
+    lisp_t *allocated = CAR(cell);
+    switch (get_tag(allocated))
+    {
+    case TAG_CONS:
+      // Delete the cons
+      free(as_cons(allocated));
+      break;
+    case TAG_VEC:
+    {
+      lvec_t *lvec = as_vec(allocated);
+      vec_free(&lvec->data);
+      free(lvec);
+      break;
+    }
+    case TAG_NIL:
+    case TAG_INT:
+    case TAG_SYM:
+    case NUM_TAGS:
+      // shouldn't be dealt with (either constant or dealt with elsewhere)
+      break;
+    }
+
+    // Then free the current cell
+    free(as_cons(cell));
+  }
+  memset(sys, 0, sizeof(*sys));
+}