perf(kaos): optimize large file reads with range and tail readers

[7Sageer]

Related Issue

Supersedes #966.

Problem

Reading large text files through LocalKaos.readLines loads the whole file into memory, and the Read tool scans the whole file even when only a small line range or tail window is needed.

What changed

• Stream UTF-8 readLines with chunk-list pending buffering, avoiding O(n²) long-line buffering and preserving BOM semantics after the first line.
• Add local metadata scan, forward range reads, and reverse tail reads; the Read tool uses them when available and falls back to the existing iterator otherwise.
• Keep non-UTF-8 reads on the decode-then-split path to preserve existing behavior.
• Add tests for streaming readLines, range/tail reads, metadata scan, and Read tool optimized paths.

Limitation:

• Currently only UTF-8 is supported.
• SSH/ACP is not supported.

Verification

• pnpm exec vitest run packages/kaos/test/local.test.ts packages/agent-core/test/tools/read.test.ts
• pnpm lint
• pnpm typecheck

[changeset-bot]

🦋 Changeset detected

Latest commit: a8ac076

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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[pkg-pr-new]

pnpm dlx https://pkg.pr.new/@moonshot-ai/kimi-code@a8ac076

npx https://pkg.pr.new/@moonshot-ai/kimi-code@a8ac076

commit: a8ac076