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.go

@@ -0,0 +1,93 @@
+package migrate
+
+import "strings"
+
+// splitSQL splits a SQL string into individual statements.
+// Handles $$ ... $$ dollar-quoted blocks, $tag$ ... $tag$ tagged quotes,
+// -- line comments, /* ... */ block comments, and '...' string literals
+// so that semicolons inside any of these constructs are not treated as
+// statement boundaries.
+func SplitSQL(sql string) []string {
+	var statements []string
+	var current strings.Builder
+	inDollarQuote := false
+	dollarTag := ""
+
+	i := 0
+	for i < len(sql) {
+		// Handle line comments (-- to end of line)
+		if !inDollarQuote && i+1 < len(sql) && sql[i] == '-' && sql[i+1] == '-' {
+			for i < len(sql) && sql[i] != '\n' {
+				current.WriteByte(sql[i])
+				i++
+			}
+			continue
+		}
+
+		// Handle block comments (/* ... */)
+		if !inDollarQuote && i+1 < len(sql) && sql[i] == '/' && sql[i+1] == '*' {
+			end := strings.Index(sql[i+2:], "*/")
+			if end >= 0 {
+				current.WriteString(sql[i : i+end+4])
+				i += end + 4
+				continue
+			}
+		}
+
+		// Handle single-quoted string literals ('...')
+		if !inDollarQuote && sql[i] == '\'' {
+			j := i + 1
+			for j < len(sql) {
+				if sql[j] == '\'' {
+					if j+1 < len(sql) && sql[j+1] == '\'' {
+						j += 2 // skip doubled quote ''
+						continue
+					}
+					break
+				}
+				j++
+			}
+			current.WriteString(sql[i : j+1])
+			i = j + 1
+			continue
+		}
+
+		// Check for dollar-quote start/end
+		if !inDollarQuote && sql[i] == '$' {
+			j := i + 1
+			for j < len(sql) && (sql[j] == '_' || (sql[j] >= 'a' && sql[j] <= 'z') || (sql[j] >= 'A' && sql[j] <= 'Z') || (sql[j] >= '0' && sql[j] <= '9')) {
+				j++
+			}
+			if j < len(sql) && sql[j] == '$' {
+				dollarTag = sql[i : j+1]
+				current.WriteString(dollarTag)
+				inDollarQuote = true
+				i = j + 1
+				continue
+			}
+		}
+		if inDollarQuote && strings.HasPrefix(sql[i:], dollarTag) {
+			current.WriteString(dollarTag)
+			i += len(dollarTag)
+			inDollarQuote = false
+			dollarTag = ""
+			continue
+		}
+
+		if !inDollarQuote && sql[i] == ';' {
+			statements = append(statements, current.String())
+			current.Reset()
+			i++
+			continue
+		}
+
+		current.WriteByte(sql[i])
+		i++
+	}
+
+	if strings.TrimSpace(current.String()) != "" {
+		statements = append(statements, current.String())
+	}
+
+	return statements
+}