`strip_string_quotes=True` turns a literal inside `%{ ... }` into a bare reference

[livingstaccato]

Summary

TemplateStringRule.serialize strips the " delimiters whenever
strip_string_quotes is set. That rule only ever appears inside a template
directive, where the text is expression source -- so the delimiters it removes
are a string literal's, not the template's.

Reproduction

hcl2.loads('a = "%{ if x == \\"y\\" }t%{ endif }"\n',
           serialization_options=SerializationOptions(strip_string_quotes=True))["a"]
# '%{ if x == y }t%{ endif }'

The literal "y" has become a reference to y: a different expression, not a
different spelling of the same one. TemplateStringRule.serialize is
hcl2/rules/strings.py:269 at v8.1.3. The source form is correct; only the
value form is affected.

Same root cause as #E above -- a rule inside expression source treating it as
literal text -- but a different rule, so it is filed separately.

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This issue, and the investigation behind it, were produced by an AI assistant (Claude) working on behalf of the author. Please review with that provenance in mind.