This PR fixes an issue where readFile and readFileSync incorrectly updated both atime (access time) and ctime (change time) when reading files. According to POSIX standards and real Node.js behavior, reading a file should only update atime, not ctime.

Problem

The issue occurred because:

1. The atime setter in Node.ts automatically updated ctime whenever atime was set
2. getBuffer() called setBuffer() when initializing empty buffers, which triggered touch() and updated both mtime and ctime

This caused memfs to behave differently from the native Node.js fs module:

// With memfs (before fix)
await fs.promises.writeFile('/test.txt', 'content');
const before = (await fs.promises.stat('/test.txt')).ctimeMs;
await fs.promises.readFile('/test.txt'); // This incorrectly updated ctime
const after = (await fs.promises.stat('/test.txt')).ctimeMs;
console.log(before !== after); // true (wrong!)

// With native Node.js fs
// The ctime remains unchanged after readFile

Solution

Core fixes:

• Removed automatic ctime update from the atime setter in src/core/Node.ts
• Fixed getBuffer() to directly initialize empty buffers without calling setBuffer() (which was triggering unnecessary touch() calls)

Test updates:

• Updated existing Node-level tests to expect correct behavior
• Added comprehensive integration tests specifically for the readFile/readFileSync ctime behavior

Result

• readFile and readFileSync now correctly update only atime when reading files
• ctime is only updated for actual metadata/content changes (chmod, chown, write operations, etc.)
• Behavior now matches real Node.js fs implementation
• All existing tests pass

The changes are minimal and surgical, affecting only the specific timestamp update logic without changing any other filesystem behavior.

Fixes #1177.

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