fix(herdr): rewrite CodexActivity against the real live rollout shape (S11)

The previous function_call/function_call_output shape was never verified
and doesn't exist in any real Codex rollout. Confirmed the real shape
against this machine's own ~/.codex/sessions files: file edits arrive as
event_msg/patch_apply_end (changes+success, no pairing needed), and shell
commands arrive as a freeform custom_tool_call named "exec" whose input is
a JS snippet embedding cmd:"..." rather than a flat arguments object, with
failure signaled by a literal "Script error:" prefix in the output text.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

internal/herdr/activity_test.go

@@ -72,6 +72,112 @@ func TestClaudeActivityPairsToolUseWithResult(t *testing.T) {
 	}
 }
 
+func codexPatchApplyLine(t *testing.T, callID string, success bool, paths ...string) string {
+	t.Helper()
+	changes := map[string]any{}
+	for _, p := range paths {
+		changes[p] = map[string]any{"type": "update"}
+	}
+	b, err := json.Marshal(map[string]any{
+		"type": "event_msg",
+		"payload": map[string]any{
+			"type":    "patch_apply_end",
+			"call_id": callID,
+			"success": success,
+			"changes": changes,
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(b)
+}
+
+func codexExecCallLine(t *testing.T, callID, input string) string {
+	t.Helper()
+	b, err := json.Marshal(map[string]any{
+		"type": "response_item",
+		"payload": map[string]any{
+			"type":    "custom_tool_call",
+			"call_id": callID,
+			"name":    "exec",
+			"input":   input,
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(b)
+}
+
+func codexExecOutputLine(t *testing.T, callID string, texts ...string) string {
+	t.Helper()
+	var out []map[string]any
+	for _, tx := range texts {
+		out = append(out, map[string]any{"type": "input_text", "text": tx})
+	}
+	b, err := json.Marshal(map[string]any{
+		"type": "response_item",
+		"payload": map[string]any{
+			"type":    "custom_tool_call_output",
+			"call_id": callID,
+			"output":  out,
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(b)
+}
+
+// Fixture shape confirmed live against this machine's own ~/.codex/sessions
+// rollout files on 2026-07-28 (see activity.go's CodexActivity doc comment) —
+// not a guess at the schema.
+func TestCodexActivityParsesRealRolloutShape(t *testing.T) {
+	path := writeJSONL(t, []string{
+		codexExecCallLine(t, "c1", `const r = await tools.exec_command({cmd:"go test ./...","workdir":"/repo"}); text(r.output)`),
+		codexExecOutputLine(t, "c1", "Script completed\nWall time 0.1 seconds\nOutput:\n", "FAIL"),
+		codexExecCallLine(t, "c2", `const r = await tools.exec_command({cmd:"git commit -am x"}); text(r.output)`),
+		codexExecOutputLine(t, "c2", "Script completed\n"),
+		codexPatchApplyLine(t, "exec-1", true, "/repo/main.go"),
+		codexExecCallLine(t, "c3", `const r = await tools.update_plan({plan:[]}); text(r)`),
+		codexExecOutputLine(t, "c3", "Script error:\nSyntaxError: bad"),
+	})
+	calls, err := CodexActivity(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(calls) != 4 {
+		t.Fatalf("calls=%+v, want 4 (update_plan call resolved with empty kind/key, not dropped)", calls)
+	}
+	if calls[3].Kind != "" || calls[3].Key != "" {
+		t.Fatalf("calls[3]=%+v, want empty kind/key for a call with no embedded cmd:", calls[3])
+	}
+	if calls[0].Kind != "command" || calls[0].Key != "go test ./..." || !calls[0].IsTest || !calls[0].Success {
+		t.Fatalf("calls[0]=%+v", calls[0])
+	}
+	if calls[1].Kind != "command" || calls[1].Key != "git commit -am x" || !calls[1].Success {
+		t.Fatalf("calls[1]=%+v", calls[1])
+	}
+	if calls[2].Kind != "file" || calls[2].Key != "/repo/main.go" || !calls[2].Success {
+		t.Fatalf("calls[2]=%+v", calls[2])
+	}
+}
+
+func TestCodexActivityMarksScriptErrorAsFailure(t *testing.T) {
+	path := writeJSONL(t, []string{
+		codexExecCallLine(t, "c1", `const r = await tools.exec_command({cmd:"pytest"}); text(r.output)`),
+		codexExecOutputLine(t, "c1", "Script error:\napply_patch verification failed"),
+	})
+	calls, err := CodexActivity(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(calls) != 1 || calls[0].Success {
+		t.Fatalf("calls=%+v, want one failed call", calls)
+	}
+}
+
 func TestDetectThrashConsecutiveTestFailures(t *testing.T) {
 	calls := []ToolCall{
 		{Name: "Bash", Kind: "command", Key: "go test ./...", Success: false, IsTest: true},