feat(go): durable transaction engine and Kiro IDE 1.0 adapter

Split the monolithic transaction into focused modules: append-only
crash-recoverable journal under ~/.elydora/transactions with owner
tokens and per-transaction namespaces, staged atomic publication
(stage .pending, fsync, rename, fsync), platform-specific atomic
replacement (MoveFileEx, renameat2, renamex_np), private-directory
hardening per OS, lock-guarded recovery, and workspace cleanup that
removes only transaction-created empty directories.

Add the Kiro IDE 1.0 plugin: strict v1 hook schema with one enabled
PreToolUse guard and PostToolUse audit pair bound to the active
workspace, agent-to-workspace identity binding in runtime config, and
exact migration of the legacy elydora-audit.kiro.hook contract.

Gates: go test ./... and -race pass, go vet clean, govulncheck reports
zero reachable vulnerabilities, git diff --check clean.

cmd/elydora/plugins/transaction_private_unix.go

@@ -0,0 +1,78 @@
+//go:build linux || darwin
+
+package plugins
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"syscall"
+)
+
+func createPrivateTransactionDirectory(path string) error {
+	if err := os.Mkdir(path, 0700); err != nil {
+		return err
+	}
+	return verifyPrivateTransactionDirectory(path)
+}
+
+func ensurePrivateTransactionDirectory(path string) error {
+	info, err := os.Lstat(path)
+	if errors.Is(err, os.ErrNotExist) {
+		if createErr := createPrivateTransactionDirectory(path); createErr == nil {
+			return nil
+		} else if !errors.Is(createErr, os.ErrExist) {
+			return createErr
+		}
+		info, err = os.Lstat(path)
+	}
+	if err != nil {
+		return err
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return fmt.Errorf("transaction namespace is not a physical directory: %s", path)
+	}
+	return verifyPrivateTransactionDirectory(path)
+}
+
+func verifyPrivateTransactionDirectory(path string) error {
+	info, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return fmt.Errorf("transaction namespace is not owner-only: %s", path)
+	}
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	if !ok || stat.Uid != uint32(os.Geteuid()) {
+		return fmt.Errorf("transaction namespace owner does not match effective user: %s", path)
+	}
+	if err := hardenPrivateTransactionDirectory(path); err != nil {
+		return err
+	}
+	info, err = os.Lstat(path)
+	if err != nil || info.Mode()&os.ModeSymlink != 0 || !info.IsDir() ||
+		info.Mode().Perm() != 0700 {
+		return errors.Join(fmt.Errorf("transaction namespace is not owner-only: %s", path), err)
+	}
+	stat, ok = info.Sys().(*syscall.Stat_t)
+	if !ok || stat.Uid != uint32(os.Geteuid()) {
+		return fmt.Errorf("transaction namespace owner does not match effective user: %s", path)
+	}
+	return nil
+}
+
+func verifyTransactionNamespaceParent(path string) error {
+	info, err := os.Lstat(path)
+	if err != nil || info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return errors.Join(fmt.Errorf("transaction namespace parent is not a physical directory: %s", path), err)
+	}
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	if !ok || stat.Uid != uint32(os.Geteuid()) {
+		return fmt.Errorf("transaction namespace parent owner does not match effective user: %s", path)
+	}
+	if info.Mode().Perm()&0022 != 0 {
+		return fmt.Errorf("transaction namespace parent is writable by another user: %s", path)
+	}
+	return nil
+}