feat(core,router): expose Context and add LinearRouter.matchRoute utility

[Digital39999]

This PR introduces two public APIs that were previously internal.
It also resolves #4409.

• Context class - exported from index.ts for advanced use cases (testing, unified request handling, extensions).

• LinearRouter.matchRoute static method

  • Abstraction of the internal matching logic.
  • Allows for comprehensive testing and reusability of route-matching behavior.
  • Covers exact paths, wildcards, parameters, regex patterns, edge cases, and unsupported patterns.

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The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code