fix(agent-core-v2): follow symlinks when loading AGENTS.md and reading files

[7Sageer]

Related Issue

None — the problem is described below.

Problem

The v2 engine's filesystem stat used lstat semantics, so symbolic links were never counted as regular files. Two user-visible consequences in the web backend (a common dotfiles setup is installing config/instruction files as symlinks):

• AGENTS.md instruction files installed as symlinks were silently dropped while assembling the system prompt.
• The Read tool rejected symlinked files with "<path>" is not a file., and ReadMediaFile size checks measured the symlink itself instead of its target.

The CLI (v1 engine) follows symlinks and handles such files correctly, so CLI and web behavior diverged.

What changed

• IHostFileSystem.stat accepts an optional followSymlinks flag; the default keeps the previous lstat semantics, so other consumers (e.g. directory listings that need to detect symlinks) are unaffected.
• The AGENTS.md loader, Read, and ReadMediaFile now stat with followSymlinks, matching the v1 CLI behavior.
• Added regression tests covering symlinked user-level and project-level AGENTS.md files, plus an assertion that the Read tool stats with followSymlinks.

Skill discovery and MCP config loading were audited for the same problem and are not affected: they use node:fs directly, which already follows symlinks.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

[changeset-bot]

🦋 Changeset detected

Latest commit: 73f77fc

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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commit: 73f77fc