refactor+test: persona data table, parser fuzz targets, hot-path benchmarks

.github/workflows/ci.yml

@@ -558,6 +558,8 @@ jobs:
           go test -run='^$' -fuzz=FuzzParseMessage       -fuzztime=60s ./internal/session
           go test -run='^$' -fuzz=FuzzParseSessionMeta   -fuzztime=60s ./internal/session
           go test -run='^$' -fuzz=FuzzParseDeltaSpec    -fuzztime=60s ./internal/spec
+          go test -run='^$' -fuzz=FuzzParseSearchReplace -fuzztime=60s ./internal/engine/diff
+          go test -run='^$' -fuzz=FuzzParseToolCallResult -fuzztime=60s ./internal/mcp
 
   # -------------------------------------------------------------------------
   # 10. Smoke — build rho and verify ecosystem CLI wiring.

internal/engine/diff/searchreplace_fuzz_test.go

@@ -0,0 +1,26 @@
+package diff
+
+import "testing"
+
+// FuzzParseSearchReplace ensures the SEARCH/REPLACE parser and applier never
+// panic on arbitrary model output.
+func FuzzParseSearchReplace(f *testing.F) {
+	f.Add("<<<<<<< SEARCH\nold\n=======\nnew\n>>>>>>> REPLACE")
+	f.Add("")
+	f.Add("<<<<<<< SEARCH\nonly a search\n>>>>>>> REPLACE")
+	f.Add("prose before\n<<<<<<< SEARCH\na\n=======\nb\n>>>>>>> REPLACE\nprose after")
+
+	f.Fuzz(func(t *testing.T, text string) {
+		blocks := ParseSearchReplace(text)
+		_, _ = ApplySearchReplace("old\ncontent\n", blocks)
+		_, _ = ApplySearchReplace("", blocks)
+	})
+}
+
+func BenchmarkParseSearchReplace(b *testing.B) {
+	const in = "prose\n<<<<<<< SEARCH\nold\n=======\nnew\n>>>>>>> REPLACE\n"
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		_ = ParseSearchReplace(in)
+	}
+}

internal/mcp/mcp_fuzz_test.go

@@ -0,0 +1,19 @@
+package mcp
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// FuzzParseToolCallResult ensures the MCP tool-result parser never panics on
+// arbitrary server responses.
+func FuzzParseToolCallResult(f *testing.F) {
+	f.Add([]byte(`{"content":[{"type":"text","text":"hi"}]}`))
+	f.Add([]byte(`{"content":[{"type":"image","data":"..."}],"isError":true}`))
+	f.Add([]byte(`not json`))
+	f.Add([]byte(`{"content":[{"type":"text","text":"a"},{"type":"text","text":"b"}]}`))
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		_, _ = parseToolCallResult(json.RawMessage(b))
+	})
+}