fix: handle newline characters in specLiteralStringCode

[t-unit]

Summary

• specLiteralStringCode() now skips single-line raw strings (r'...', r"...") when the value contains \n or \r, using triple-quoted raw strings or the escaped fallback path instead
• escapeForSingleQuotedDartString() now escapes \n and \r so the fallback path produces valid Dart
• Added 9 new tests covering \n, \r, \r\n, and combinations with quotes

Test plan

• All 1,899 tonik_generate unit tests pass (including 9 new newline tests)
• All 3,727 unit tests pass across all packages
• All 3,450 integration tests pass across 27 suites
• fvm dart analyze clean

Closes #88

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.76%. Comparing base (3563c8e) to head (227d8ef).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #89   +/-   ##
=======================================
  Coverage   89.75%   89.76%           
=======================================
  Files         157      157           
  Lines       14479    14483    +4     
=======================================
+ Hits        12996    13000    +4     
  Misses       1483     1483           

Files with missing lines	Coverage Δ
...nik_generate/lib/src/util/spec_literal_string.dart	100.00% <100.00%> (ø)

Files with missing lines	Coverage Δ
...nik_generate/lib/src/util/spec_literal_string.dart	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

Fixes Dart code generation for OpenAPI spec string values containing newline characters by preventing invalid single-line raw string literals and ensuring the escaped fallback path produces syntactically valid Dart.

Changes:

• Updated specLiteralStringCode() to avoid single-line raw strings when the input contains \n or \r, preferring raw triple-quoted strings when viable.
• Updated escapeForSingleQuotedDartString() to escape \n and \r so fallback (non-raw) literals remain valid.
• Added unit tests covering \n, \r, \r\n, and newline interactions with quotes / """ edge cases.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/tonik_generate/lib/src/util/spec_literal_string.dart	Adjusts quoting/escaping strategy to handle newline characters safely in generated Dart string literals.
packages/tonik_generate/test/src/util/spec_literal_string_test.dart	Adds focused tests validating the new newline handling and escaping behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.