test: add comprehensive unit tests for src/utils/index.ts

[GoBeromsu]

Summary

• Added 38 comprehensive unit tests for src/utils/index.ts
• Achieves 100% code coverage across all metrics (statements, branches, functions, lines)
• All tests follow existing patterns with Jest and descriptive naming conventions

Test Coverage

PROVIDER_NAMES (3 tests)

• Validates all 8 provider constants match JSON data
• Verifies correct provider name values
• Tests constant immutability

generateId() (4 tests)

• Returns a number type
• Returns current timestamp
• Generates unique/increasing IDs
• Handles async ID generation

getProviderPresets() (5 tests)

• Returns array of presets
• Contains all 8 expected providers
• Each preset has required ProviderPreset properties
• Excludes apiKey property correctly

getProviderPreset() (12 tests)

• Successfully retrieves each of 8 providers by name
• Throws descriptive errors for non-existent providers
• Case-sensitive name matching
• Validates popularModels structure

findMatchingPreset() (14 tests)

• Matches by exact baseUrl
• Matches by exact name
• Prioritizes baseUrl over name
• Returns 'Custom Provider' for non-matches
• Tests all providers
• Case-sensitive matching
• No partial URL matching

Test Results

Test Suites: 1 passed, 1 total
Tests:       38 passed, 38 total
Coverage:    100% (Statements, Branches, Functions, Lines)

Test Plan

• All new tests pass
• Existing tests still pass (113 total)
• 100% code coverage achieved
• Tests follow existing patterns in codebase
• Descriptive test names and organized with describe blocks
• Tests cover edge cases and error conditions

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