engram: WAL persistence + integrity hardening + single canonical runtime

Establish lang/runtime/ as the ONE canonical el runtime (from the active
runtime that carries hebb/emb persistence + the new WAL); repoint the el CI
publish, engram build, elb default, and in-repo build scripts to it; delete
the el-compiler/runtime + lang/releases/ forks; add scripts/check-single-runtime.sh
drift guard.

Fixes a live prod bug: the el CI published el-runtime-c/-h from the LAGGING
el-compiler fork (0 hebb refs), so the shipped soul never persisted Hebbian
edge weights — learned co-activation was wiped on every restart. Publishing
from canonical ships the stranded 'learning that cannot outlive the process'
fix.

WAL storage engine + integrity fixes (DELETE->tombstone + store-layer
protection, safe data-dir default) ride in behind ENGRAM_WAL (default off =
byte-identical to today). Verified: engram elb per-module build clean, WAL
gate 66/66, native smoke ok, drift-guard green.

lang/elb.el

@@ -368,13 +368,13 @@ fn main() -> Void {
         let which_out: String = str_trim(exec_capture("which " + elc_bin + " 2>/dev/null"))
         if !str_eq(which_out, "") {
             let elc_dir: String = dirname_of(which_out)
-            runtime_path = elc_dir + "/../el-compiler/runtime/el_runtime.c"
+            runtime_path = elc_dir + "/../runtime/el_runtime.c"
         }
     }
     // If --runtime points to a directory, auto-locate el_runtime.c inside it.
     // This lets both forms work:
-    //   --runtime=/opt/el/el-compiler/runtime          (directory form)
-    //   --runtime=/opt/el/el-compiler/runtime/el_runtime.c  (file form)
+    //   --runtime=/opt/el/runtime          (directory form)
+    //   --runtime=/opt/el/runtime/el_runtime.c  (file form)
     if !str_eq(runtime_path, "") {
         let is_dir: String = str_trim(exec_capture("test -d " + runtime_path + " && echo dir || echo file"))
         if str_eq(is_dir, "dir") {