feat(benchmarks): add hashline-edit test suites (46 tests)
Ported from code-editing-agent benchmark:
- test-edit-ops.ts: 21 basic edit operations (replace, append, prepend, delete, batch, range)
- test-edge-cases.ts: 25 edge cases (unicode, long lines, whitespace, special chars, file creation)
- test-multi-model.ts: multi-model comparison runner
Verified 21/21 + 25/25 (100%) with Minimax M2.5 via FriendliAI.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
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