feat: unify MODIFY ATTRIBUTE syntax to accept colon separator (#81)

The MODIFY ATTRIBUTE syntax was inconsistent with CREATE ENTITY and
ADD ATTRIBUTE which both use colon (Name: Type). MODIFY ATTRIBUTE
used space (Name Type).

Update the grammar to accept an optional colon in MODIFY ATTRIBUTE
and MODIFY COLUMN, making colon the recommended style:

  ALTER ENTITY Module.Customer
    MODIFY ATTRIBUTE Address: String(500);

Both syntaxes remain valid for backward compatibility:
  MODIFY ATTRIBUTE Name: String(200)   -- new (preferred)
  MODIFY ATTRIBUTE Name String(200)    -- old (still accepted)

Updated all examples and skills to use colon consistently, aligning
with CREATE ENTITY, ADD ATTRIBUTE, microflow parameters, and page
parameters.

Fixes #81

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

Author: ako

docs/06-mdl-reference/grammar-reference.md

@@ -2877,8 +2877,8 @@ alterEntityAction
     | | ADD COLUMN attributeDefinition
     | | RENAME ATTRIBUTE IDENTIFIER TO IDENTIFIER
     | | RENAME COLUMN IDENTIFIER TO IDENTIFIER
-    | | MODIFY ATTRIBUTE IDENTIFIER dataType attributeConstraint*
-    | | MODIFY COLUMN IDENTIFIER dataType attributeConstraint*
+    | | MODIFY ATTRIBUTE IDENTIFIER ':'? dataType attributeConstraint*
+    | | MODIFY COLUMN IDENTIFIER ':'? dataType attributeConstraint*
     | | DROP ATTRIBUTE IDENTIFIER
     | | DROP COLUMN IDENTIFIER
     | | SET DOCUMENTATION STRING_LITERAL

mdl-examples/doctype-tests/01-domain-model-examples.mdl

@@ -1363,11 +1363,11 @@ ALTER ENTITY DmTest.Settings
 
 -- Widen a string attribute.
 ALTER ENTITY DmTest.Document
-  MODIFY ATTRIBUTE Summary String(1000);
+  MODIFY ATTRIBUTE Summary: String(1000);
 
 -- Change multiple attribute types in one statement.
 ALTER ENTITY DmTest.SimpleTag
-  MODIFY ATTRIBUTE Name String(200);
+  MODIFY ATTRIBUTE Name: String(200);
 
 -- ============================================================================
 -- Level 10.4: DROP ATTRIBUTE

mdl/grammar/MDLParser.g4

@@ -696,8 +696,8 @@ alterEntityAction
     | ADD COLUMN attributeDefinition
     | RENAME ATTRIBUTE attributeName TO attributeName
     | RENAME COLUMN attributeName TO attributeName
-    | MODIFY ATTRIBUTE attributeName dataType attributeConstraint*
-    | MODIFY COLUMN attributeName dataType attributeConstraint*
+    | MODIFY ATTRIBUTE attributeName COLON? dataType attributeConstraint*
+    | MODIFY COLUMN attributeName COLON? dataType attributeConstraint*
     | DROP ATTRIBUTE attributeName
     | DROP COLUMN attributeName
     | SET DOCUMENTATION STRING_LITERAL