feat: Phase 8 — nomos packages extracted into internal/nomos/{turngate,retrycap,messagequeue,assent,session}

Mechanical extraction of nomos internal components into plain-Go subpackages
per the hexagonal plan (ADR 0016 §3.1 rule 3):
  turngate/   — per-session turn serialization (plan 2026-08-03 F1)
  retrycap/   — per-turn run retry cap (maxRunRetries=3)
  messagequeue/ — operator-message queue for busy-turn re-entry (F2)
  assent/     — chat-assent detection (isAssent, isTypedConfirmation,
                ExtractPendingApprovals), decoupled from agent via
                []string input instead of persistedCall
  session/    — store (chat sessions, plan execution, DB persistence),
                migration runner + local emitEvent to break adapter
                dependency

internal/migrate/ — shared migration runner extracted from postgres pool,
                    used by both the oikos postgres adapter and session tests.

session package export-rename finishing touches remain; the four smaller
packages compile with passing tests. Depguard rules and ADR-0016 leaf-note
update deferred to a followup. VERSION 0.35.1.

internal/migrate/split_test.go

@@ -0,0 +1,107 @@
+package migrate
+
+import (
+	"strings"
+	"testing"
+)
+
+func nonEmpty(stmts []string) []string {
+	var out []string
+	for _, s := range stmts {
+		if strings.TrimSpace(s) != "" {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+func TestSplitSQLBasic(t *testing.T) {
+	stmts := nonEmpty(SplitSQL("CREATE TABLE a (id int); CREATE TABLE b (id int);"))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLDollarQuotedFunction(t *testing.T) {
+	sql := `CREATE FUNCTION f() RETURNS int AS $$
+  SELECT 1; SELECT 2;
+$$ LANGUAGE sql;
+CREATE TABLE t (id int);`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+	if !strings.Contains(stmts[0], "SELECT 1; SELECT 2;") {
+		t.Errorf("dollar-quoted body was split: %q", stmts[0])
+	}
+}
+
+func TestSplitSQLTaggedDollarQuote(t *testing.T) {
+	sql := `DO $body$ BEGIN PERFORM 1; END $body$;SELECT 1;`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLSemicolonInComment(t *testing.T) {
+	sql := "-- comment with ; semicolon\nCREATE TABLE t (id int); -- trailing; note\nSELECT 1;"
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLSemicolonInStringLiteral(t *testing.T) {
+	sql := `SELECT 'hello; world'; INSERT INTO t VALUES (1);`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLDollarSignInStringLiteral(t *testing.T) {
+	sql := `SELECT '$100'; SELECT 2;`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLBlockComment(t *testing.T) {
+	sql := `SELECT 1; /* block; with; semicolons */ SELECT 2;`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLBlockCommentWithDollarQuote(t *testing.T) {
+	sql := `/* $$ not a dollar quote */ SELECT 1;`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 1 {
+		t.Fatalf("got %d statements, want 1: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLDoubledQuoteInString(t *testing.T) {
+	sql := `SELECT 'O''Brien'; SELECT 2;`
+	stmts := nonEmpty(SplitSQL(sql))
+	if len(stmts) != 2 {
+		t.Fatalf("got %d statements, want 2: %#v", len(stmts), stmts)
+	}
+}
+
+func TestSplitSQLEmptyInput(t *testing.T) {
+	stmts := nonEmpty(SplitSQL(""))
+	if len(stmts) != 0 {
+		t.Fatalf("got %d statements, want 0", len(stmts))
+	}
+}
+
+func TestSplitSQLNoSemicolon(t *testing.T) {
+	stmts := nonEmpty(SplitSQL("SELECT 1"))
+	if len(stmts) != 1 {
+		t.Fatalf("got %d statements, want 1", len(stmts))
+	}
+}