Parser: anonymous struct types in return-type position

Problem

The parser rejects anonymous struct types when they appear as a function return type:

export fn getCursor(): struct { x: usize, y: usize } {
    return .{ .x = column, .y = row }
}

Diagnostic: error[EP0001]: Expected type name.

The parser's return-type slot only accepts named types and certain primitive constructions; it doesn't recurse into a full type expression, so struct { ... } is not recognized.

Affected kernel files

• kernel/src/vga.home:213
• kernel/src/heap.home:169
• kernel/src/i18n/messages.home:663

(Subset of the 7-file 'Expected type name' bucket. The other 4 are different root causes — extern \"C\" fn(...) etc. — and will be filed separately if they cluster.)

Expected behavior

In return-type position, accept the same type grammar as in let x: T = ... annotations, including:

• struct { f1: T1, f2: T2 } (anonymous struct)
• nested generics, pointers, optionals, etc. that already work elsewhere

The returned struct-literal .{ .x = ..., .y = ... } should continue to coerce into the inferred anonymous struct type.

Implementation hint

Likely a one-line change in the return-type parsing path to call the full parseType entry point instead of parseTypeName/parsePrimitiveTypeName.

Tests to add

• Positive: anonymous struct return type with inferred field order
• Negative: malformed anonymous struct (missing field type) yields a clean diagnostic

Acceptance

1. The 3 listed kernel files clear home-debug ast.
2. Existing test suite green.