tcl: Phase 3 OCaml primitives — file-read/write/append/exists?/glob + clock-seconds/milliseconds/format in sx_primitives.ml + unix dep; tcl-cmd-clock/file wired up; 337/337 green

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

lib/tcl/tests/coro.sx

@@ -95,15 +95,15 @@
       (get (run "proc g {} { yield }\ncoroutine cg g\ncg") :result)
       "")
 
-    ; --- clock seconds stub ---
+    ; --- clock seconds ---
     (ok "clock-seconds"
-      (get (run "clock seconds") :result)
-      "0")
+      (> (parse-int (get (run "clock seconds") :result)) 0)
+      true)
 
-    ; --- clock milliseconds stub ---
+    ; --- clock milliseconds ---
     (ok "clock-milliseconds"
-      (get (run "clock milliseconds") :result)
-      "0")
+      (> (parse-int (get (run "clock milliseconds") :result)) 0)
+      true)
 
     ; --- clock format stub ---
     (ok "clock-format"