fix: update _Transaction table after MPR v2 writes for Studio Pro F4 sync (#78)

MPR v2 projects have a _Transaction table with a LastTransactionID
column. Studio Pro writes a new UUID on every save and uses it to
detect external changes during F4 sync. mxcli never updated this
table, causing Studio Pro to throw InvalidOperationException when
pressing F4 after mxcli modified the project.

Add updateTransactionID() that writes a new UUID to _Transaction
after every insertUnit, updateUnit, and deleteUnit on v2 projects.

Fixes #78

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ako

sdk/mpr/writer_units.go

@@ -13,6 +13,17 @@ import (
 	"github.com/mendixlabs/mxcli/sdk/domainmodel"
 )
 
+// updateTransactionID updates the _Transaction table with a new UUID.
+// Studio Pro uses this to detect external changes during F4 sync.
+// Only applies to MPR v2 projects (Mendix >= 10.18).
+func (w *Writer) updateTransactionID() {
+	if w.reader.version != MPRVersionV2 {
+		return
+	}
+	newID := generateUUID()
+	_, _ = w.reader.db.Exec(`UPDATE _Transaction SET LastTransactionID = ?`, newID)
+}
+
 // placeholderBinaryPrefix is the GUID-swapped byte pattern for placeholder IDs generated
 // by sdk/widgets/augment.go placeholderID(). These are "aa000000000000000000000000XXXXXX"
 // hex strings which, after hex decode + GUID byte-swap, produce 16-byte blobs whose first
@@ -70,6 +81,7 @@ func (w *Writer) insertUnit(unitID, containerID, containmentName, unitType strin
 		`, unitIDBlob, containerIDBlob, containmentName, contentsHash)
 		if err == nil {
 			w.reader.InvalidateCache()
+			w.updateTransactionID()
 		}
 		return err
 	}
@@ -126,6 +138,7 @@ func (w *Writer) updateUnit(unitID string, contents []byte) error {
 		`, contentsHash, unitIDBlob)
 		if err == nil {
 			w.reader.InvalidateCache()
+			w.updateTransactionID()
 		}
 		return err
 	}
@@ -182,6 +195,7 @@ func (w *Writer) deleteUnit(unitID string) error {
 	}
 
 	w.reader.InvalidateCache()
+	w.updateTransactionID()
 	return nil
 }