feat(soul): Layer 3 — imprint.el with bounded API surface

imprint.el

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+// Layer 3 — Imprint
+// Domain knowledge, voice, and tools bounded by the L2 stewardship surface.
+// Imprints cannot write BellEvent or StewardshipEvent nodes.
+// Lower layers (L0 core, L1 safety, L2 stewardship) are structurally inaccessible from here.
+
+// imprint_current — returns the active imprint ID from state.
+// Falls back to "base" (bare Neuron, no suit) when nothing is loaded.
+fn imprint_current() -> String {
+    let id: String = state_get("active_imprint_id")
+    return if str_eq(id, "") { "base" } else { id }
+}
+
+// imprint_load — activate an imprint by ID.
+// Searches engram for a node labelled "imprint:<id>".
+// On success: sets active_imprint_id state and returns {"ok":true,"id":"<id>"}.
+// On miss: returns {"ok":false,"error":"imprint not found: <id>"}.
+fn imprint_load(imprint_id: String) -> String {
+    let label: String = "imprint:" + imprint_id
+    let results: String = engram_search_json(label, 1)
+    let found: Bool = !str_eq(results, "") && !str_eq(results, "[]")
+    if found {
+        state_set("active_imprint_id", imprint_id)
+        return "{\"ok\":true,\"id\":\"" + imprint_id + "\"}"
+    }
+    return "{\"ok\":false,\"error\":\"imprint not found: " + imprint_id + "\"}"
+}
+
+// imprint_respond — route steward-aligned input through the active imprint's voice/domain context.
+// If imprint_id is "base" or empty: pass input through unchanged (base Neuron, no suit).
+// If the imprint node is found: annotate the input with imprint context.
+// If the node is missing: graceful fallback to base — never hard-fail at L3.
+fn imprint_respond(input: String, imprint_id: String) -> String {
+    let is_base: Bool = str_eq(imprint_id, "base") || str_eq(imprint_id, "")
+    if is_base {
+        return input
+    }
+    let label: String = "imprint:" + imprint_id
+    let results: String = engram_search_json(label, 1)
+    let found: Bool = !str_eq(results, "") && !str_eq(results, "[]")
+    if found {
+        return input + " [imprint:" + imprint_id + " active]"
+    }
+    // Graceful fallback: imprint node missing, return input unchanged
+    return input
+}
+
+// imprint_surface_knowledge — domain-scoped knowledge search for the active imprint.
+// Imprints can search knowledge but only domain-relevant nodes.
+// For "base" imprint: full query, no scope restriction.
+// For named imprints: query is narrowed to "domain:<imprint_id>" scope.
+fn imprint_surface_knowledge(query: String, imprint_id: String) -> String {
+    let is_base: Bool = str_eq(imprint_id, "base") || str_eq(imprint_id, "")
+    let scoped_query: String = if is_base {
+        query
+    } else {
+        query + " domain:" + imprint_id
+    }
+    return engram_search_json(scoped_query, 10)
+}
+
+// imprint_surface_memory_read — imprints can read memories from engram.
+// Read-only: no write surface is exposed here.
+// Imprints CANNOT write BellEvent, StewardshipEvent, or InternalStateEvent nodes —
+// those write paths are sealed in L1 and L2, which are structurally inaccessible.
+fn imprint_surface_memory_read(query: String) -> String {
+    return engram_search_json(query, 10)
+}
+
+// imprint_unload — deactivate the current imprint, returning to base Neuron.
+fn imprint_unload() -> Void {
+    state_set("active_imprint_id", "")
+}

imprint.elh

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+// auto-generated by elc --emit-header — do not edit
+extern fn imprint_current() -> String
+extern fn imprint_load(imprint_id: String) -> String
+extern fn imprint_respond(input: String, imprint_id: String) -> String
+extern fn imprint_surface_knowledge(query: String, imprint_id: String) -> String
+extern fn imprint_surface_memory_read(query: String) -> String
+extern fn imprint_unload() -> Void