Fix code search context line parsing

[hiSandog]

Summary

• Parse code_search context lines using known match file paths so hyphenated paths like src/component-2-test.ts are not truncated
• Preserve context content that also contains hyphen-number-hyphen sequences
• Add regression coverage for both cases

Validation

• git diff --check
• Attempted: ./.bin/bun test common/src/util/tests/format-code-search.test.ts (blocked locally because the repository wrapper requires .env.local/Infisical and no real bun executable is installed on PATH)