Preserve failAfter directive in isoltest ASTJSON reformatting

[tavian-dev]

Description

Fixes #14093.

When isoltest updates test expectations for ASTJSON tests (via --accept-updates), it calls ASTJSONTest::printSource() to rewrite the .sol input file. The function was not outputting the failAfter directive that was parsed and stored in m_expectedFailAfter, causing the directive to be silently dropped during reformatting.

The Fix

Added output of the failAfter directive in ASTJSONTest::printSource() when m_expectedFailAfter has a value. The directive is written in the same format that fillSources() parses: // failAfter: <CompilerState>.

Changes

• test/libsolidity/ASTJSONTest.cpp: Add failAfter output to printSource() (3 lines)

Testing

• Built and ran ASTJSON tests (72 pass)
• Built and ran syntax tests (3551 pass)
• Code style check passes
• The fix is minimal and directly addresses the parsing/output asymmetry identified in the issue

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