Add alias support for enum parsing

[umputun]

Summary

• Adds support for comment annotations on enum constants to define parsing aliases
• Enables parsing multiple string representations for the same enum value
• Fixes bug where lowercase mode didn't properly normalize input for case-insensitive parsing
• Parsing is now always case-insensitive regardless of -lower flag

Changes

• parseAliasComment() function extracts aliases from inline comments
• validateAliases() method checks for conflicts with canonical names and duplicate aliases
• Template updated to include aliases in parse map with duplicate key prevention
• Parsing always uses strings.ToLower(v) for case-insensitive lookup
• Comprehensive tests added (99.3% coverage)
• README updated with alias documentation

[Copilot]

Pull request overview

This PR adds support for parsing aliases on enum constants, enabling multiple string representations to map to the same enum value. The implementation also fixes a bug where case-insensitive parsing wasn't working correctly in lowercase mode.

Key Changes:

• Added parseAliasComment() function to extract aliases from inline comments using enum:alias= directive
• Added validateAliases() to prevent duplicate aliases and conflicts with canonical names
• Modified parsing to always be case-insensitive using strings.ToLower(v) regardless of -lower flag
• Updated template to include aliases in parse map with duplicate key prevention logic
• Added comprehensive test coverage for alias functionality

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/generator/generator.go	Core implementation of alias parsing, validation, and storage in constValue/Value structs
internal/generator/enum.go.tmpl	Updated template to generate parse map with aliases and always use case-insensitive lookup
internal/generator/generator_test.go	Added comprehensive unit tests for alias parsing, validation, and generation
internal/generator/integration_test.go	Added integration test for alias functionality
internal/generator/testdata/integration/status_enum.go	Updated generated code to reflect new case-insensitive parsing behavior
internal/generator/testdata/integration/priority_enum.go	Fixed import ordering (standard library before third-party)
internal/generator/testdata/integration/permission.go	Added test enum with aliases for integration testing
README.md	Added comprehensive documentation for alias feature with examples and usage rules

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