augmentExportEquals2 fixture has a duplicate @filename directive #64927

The augmentExportEquals2 conformance fixture contains two consecutive // @filename: file3.ts directives. The harness saves the previous unit with empty content when it encounters a new @filename directive and then reopens the same name, so the content-bearing file3.ts is wiped and the test silently expects zero errors.

This is the fixture-only half of #63814, as diagnosed by Anders Hejlsberg (@ahejlsberg): #63814 (comment). The semantic exportAssignmentMembersVisibleInAugmentation work remains in #63814.

PR #64748 removes the duplicate directive, restores the full three-file program, and updates the baselines.