[patch] Stop [PrefixAndSuffix] letting the prefix and suffix overlap, and reject empty strings

[matt-edmondson]

Fixes #338

What was wrong

PrefixAndSuffixAttribute had two problems:

• Overlap. It checked StartsWith(prefix) and EndsWith(suffix) independently, so the same characters could count as both. A lone " passed [PrefixAndSuffix("\"", "\"")], and "aba" passed [PrefixAndSuffix("ab", "ba")].
• Empty strings. It returned success for an empty string, unlike [StartsWith] and [EndsWith], which reject one.

Change (Semantics.Strings/Validation/Attributes/Text/PrefixAndSuffixAttribute.cs)

• An empty string now fails, matching the sibling attributes.
• A value shorter than prefix.Length + suffix.Length fails before the prefix and suffix checks, so each delimiter needs its own characters.
• The type's summary now states both rules.

Release note: this tightens validation. A type that relied on "" or an overlapping value being accepted will now get an ArgumentException from Create.

Tests (TextValidationAttributesTests)

• PrefixAndSuffixAttribute_LoneDelimiterServingAsBoth_ShouldThrow: " with [PrefixAndSuffix("\"", "\"")]
• PrefixAndSuffixAttribute_OverlappingPrefixAndSuffix_ShouldThrow: aba with [PrefixAndSuffix("ab", "ba")]
• PrefixAndSuffixAttribute_EmptyString_ShouldThrow
• PrefixAndSuffixAttribute_DelimitersEachPresent_ShouldPass: "" (two quotes) and "quoted" are still accepted
• PrefixAndSuffixAttribute_AdjacentPrefixAndSuffix_ShouldPass: abba is accepted, since the prefix and suffix touch but don't overlap

These are the three inputs from the issue's acceptance criteria. The existing PrefixAndSuffix_* tests, including "PrefixTestSuffix", still pass.

Verification

• With the attribute change reverted, the three rejection tests fail. With it, all 15 PrefixAndSuffix tests pass.
• The full Semantics.Test suite passes on net10.0: 1486 passed, 0 failed, 8 skipped (the same 8 are skipped on main).
• Semantics.Strings builds with the local Sonar analyzers (.sonarlint/sonar-local.props) with 0 warnings.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LoEzLXruuTHCcJnXtVa49Z

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Generated by Claude Code

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Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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