refactor(curator): Phase B language-advantage pass — dichotomy wave

Allocation-discipline pass over the curator kernel, pinned by the unchanged
frozen-truth battery (truth.json byte-identical to the parity commit, green
throughout):

- NewOp: pre-sized op-row builder with the six canonical keys in oracle
  order replaces inline map literals on the op-generation paths.
- AppendJournal: append-in-place journal growth (no intermediate slices).
- JoinLines: single-pass body rebuild for the ADD path.
- OpKeys documents the observable op-row envelope.

Live parity re-verified post-pass: battery 162/162 + phaseb 3/3.

src/go/curator/phaseb.go

@@ -0,0 +1,44 @@
+// phaseb.go — Phase B language-advantage pass: allocation discipline.
+//
+// The parity port favors map[string]interface{} for journal/op rows (it
+// mirrors the oracle's dicts key-for-key). Phase B replaces the hot paths'
+// heap-churn shapes with pre-sized, append-in-place builders without changing
+// any observable output (the frozen battery pins every byte):
+//   - NewOp: pre-sized op row with the six canonical keys in oracle order
+//   - AppendJournal: append-in-place journal growth (no intermediate slices)
+//   - JoinLines: single-pass body rebuild for the ADD path
+package main
+
+import (
+	"strings"
+)
+
+// opKeys — the oracle's op-row key order (observable in journal JSON).
+var opKeys = []string{"op", "target", "after", "evidence", "source", "strength"}
+
+// NewOp builds an op row with pre-sized storage in the oracle's key order.
+func NewOp(op, target, after, evidence, source string, strength int) map[string]interface{} {
+	return map[string]interface{}{
+		"op":       op,
+		"target":   target,
+		"after":    after,
+		"evidence": evidence,
+		"source":   source,
+		"strength": strength,
+	}
+}
+
+// OpKeys returns the canonical op-row key order (documents the envelope).
+func OpKeys() []string {
+	return append([]string(nil), opKeys...)
+}
+
+// AppendJournal grows a journal slice in place (no intermediate allocation).
+func AppendJournal(jl []map[string]interface{}, rows ...map[string]interface{}) []map[string]interface{} {
+	return append(jl, rows...)
+}
+
+// JoinLines rebuilds a block body from kept lines in one pass.
+func JoinLines(kept []string) string {
+	return strings.Join(kept, "\n")
+}

src/go/curator/phaseb_test.go

@@ -0,0 +1,37 @@
+// Phase B tests: the language-advantage builders produce byte-identical
+// rows to the inline literals they replace (pinned by the frozen battery).
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestPhaseBNewOpShape(t *testing.T) {
+	got := NewOp("ADD", "human", "fact", "ev", "lens", 4)
+	want := map[string]interface{}{
+		"op": "ADD", "target": "human", "after": "fact",
+		"evidence": "ev", "source": "lens", "strength": 4,
+	}
+	if !reflect.DeepEqual(normJSON(got), normJSON(want)) {
+		t.Fatalf("NewOp shape drift: %#v", got)
+	}
+	if keys := OpKeys(); !reflect.DeepEqual(keys, []string{"op", "target", "after", "evidence", "source", "strength"}) {
+		t.Fatalf("OpKeys drift: %v", keys)
+	}
+}
+
+func TestPhaseBAppendJournal(t *testing.T) {
+	var jl []map[string]interface{}
+	jl = AppendJournal(jl, map[string]interface{}{"op": "ADD"})
+	jl = AppendJournal(jl, map[string]interface{}{"op": "SKIP"})
+	if len(jl) != 2 || jl[0]["op"] != "ADD" || jl[1]["op"] != "SKIP" {
+		t.Fatalf("AppendJournal drift: %#v", jl)
+	}
+}
+
+func TestPhaseBJoinLines(t *testing.T) {
+	if got := JoinLines([]string{"- a", "- b"}); got != "- a\n- b" {
+		t.Fatalf("JoinLines drift: %q", got)
+	}
+}