fix(soul): address review issues in feat/layer-composition

- Add stub implementations of safety.el, stewardship.el, and imprint.el
  with their .elh headers so the branch compiles without the dependency
  branches (feat/layer-safety, feat/layer-stewardship, feat/layer-imprint).
  Each stub documents the layer contract it must satisfy when replaced.

- Fix GET /api/chat bypass: update the GET branch in handle_request to
  call layered_cycle() consistently with the POST branch, rather than
  calling handle_chat() directly and skipping the consciousness stack.

- Export layered_cycle() from soul.elh (and dist/soul.elh) so routes.el
  can resolve the symbol via the header import.

- Fix steward_action else branch: add explicit handling for "block"
  (returns safe refusal immediately, skips L3) and "redirect" (uses
  redirect_to field). Unknown actions now log a warning and fall back to
  the screened input rather than silently passing an empty string to
  imprint_respond().

- Document hard_bell path: clarify that omitting auto_persist/history
  update is intentional security isolation, and document the safety_validate
  second-param sentinel contract ("hard_bell" vs screen_action).

safety.el

@@ -0,0 +1,33 @@
+// safety.el — L1 Safety layer (stub — full implementation in feat/layer-safety)
+// Provides safety screening and validation for the consciousness stack.
+// This stub allows soul.el to compile while feat/layer-safety is pending merge.
+//
+// Contract for safety_screen(input, history) -> String (JSON):
+//   {"action": "pass" | "hard_bell", "content": "<screened input>", "reason": "<if hard_bell>"}
+//
+// Contract for safety_validate(output, screen_action) -> String:
+//   Second param is the original screen_action ("pass") or the sentinel "hard_bell".
+//   Returns the validated output string, or a safe refusal if validation fails.
+//
+// Contract for safety_log_bell(severity, reason, excerpt) -> Void:
+//   Logs a bell event to engram. severity = "hard" | "soft". Hard bell events are
+//   intentionally NOT added to conversation_history (security isolation by design).
+
+fn safety_screen(input: String, history: String) -> String {
+    return "{\"action\":\"pass\",\"content\":\"" + json_safe(input) + "\"}"
+}
+
+fn safety_validate(output: String, screen_action: String) -> String {
+    return output
+}
+
+fn safety_log_bell(severity: String, reason: String, excerpt: String) -> Void {
+    let tags: String = "[\"safety\",\"bell\",\"" + severity + "-bell\"]"
+    let payload: String = "{\"severity\":\"" + severity + "\",\"reason\":\"" + json_safe(reason) + "\",\"excerpt\":\"" + json_safe(excerpt) + "\"}"
+    let discard: String = engram_node_full(
+        payload, "InternalStateEvent", "safety:bell",
+        el_from_float(0.95), el_from_float(0.95), el_from_float(1.0),
+        "Episodic", tags
+    )
+    println("[safety] bell logged severity=" + severity + " reason=" + reason)
+}