docs: 📝 improve fs.StatFs property descriptions

Expand the descriptions for statfs.bavail, statfs.bfree, and statfs.blocks to explain how to multiply by bsize to get byte counts, and add usage examples. Expand statfs.type with an explanation of what the numeric value represents. Add a reference link for statfs.bsize to support the cross-references.

Author: aymanxdev

doc/api/fs.md

@@ -7929,7 +7929,26 @@ added:
 
 * Type: {number|bigint}
 
-Free blocks available to unprivileged users.
+Free blocks available to unprivileged users. Multiply by [`statfs.bsize`][]
+to get the number of available bytes.
+
+```mjs
+import { statfs } from 'node:fs/promises';
+
+const stats = await statfs('/');
+const availableBytes = stats.bsize * stats.bavail;
+console.log(`Available space: ${availableBytes} bytes`);
+```
+
+```cjs
+const { statfs } = require('node:fs/promises');
+
+(async () => {
+  const stats = await statfs('/');
+  const availableBytes = stats.bsize * stats.bavail;
+  console.log(`Available space: ${availableBytes} bytes`);
+})();
+```
 
 #### `statfs.bfree`
 
@@ -7941,7 +7960,26 @@ added:
 
 * Type: {number|bigint}
 
-Free blocks in file system.
+Free blocks in file system. Multiply by [`statfs.bsize`][] to get the number
+of free bytes.
+
+```mjs
+import { statfs } from 'node:fs/promises';
+
+const stats = await statfs('/');
+const freeBytes = stats.bsize * stats.bfree;
+console.log(`Free space: ${freeBytes} bytes`);
+```
+
+```cjs
+const { statfs } = require('node:fs/promises');
+
+(async () => {
+  const stats = await statfs('/');
+  const freeBytes = stats.bsize * stats.bfree;
+  console.log(`Free space: ${freeBytes} bytes`);
+})();
+```
 
 #### `statfs.blocks`
 
@@ -7953,7 +7991,26 @@ added:
 
 * Type: {number|bigint}
 
-Total data blocks in file system.
+Total data blocks in file system. Multiply by [`statfs.bsize`][] to get the
+total size in bytes.
+
+```mjs
+import { statfs } from 'node:fs/promises';
+
+const stats = await statfs('/');
+const totalBytes = stats.bsize * stats.blocks;
+console.log(`Total space: ${totalBytes} bytes`);
+```
+
+```cjs
+const { statfs } = require('node:fs/promises');
+
+(async () => {
+  const stats = await statfs('/');
+  const totalBytes = stats.bsize * stats.blocks;
+  console.log(`Total space: ${totalBytes} bytes`);
+})();
+```
 
 #### `statfs.bsize`
 
@@ -7965,7 +8022,7 @@ added:
 
 * Type: {number|bigint}
 
-Optimal transfer block size.
+Optimal transfer block size in bytes.
 
 #### `statfs.frsize`
 
@@ -8011,7 +8068,11 @@ added:
 
 * Type: {number|bigint}
 
-Type of file system.
+Type of file system. A platform-specific numeric identifier for the type of
+file system. This value corresponds to the `f_type` field returned by
+`statfs(2)` on POSIX systems (for example, `0xEF53` for ext4 on Linux). Its
+meaning is OS-dependent and is not guaranteed to be consistent across
+platforms.
 
 ### Class: `fs.Utf8Stream`
 
@@ -9060,6 +9121,7 @@ the file contents.
 [`fsPromises.rm()`]: #fspromisesrmpath-options
 [`fsPromises.stat()`]: #fspromisesstatpath-options
 [`fsPromises.utimes()`]: #fspromisesutimespath-atime-mtime
+[`statfs.bsize`]: #statfsbsize
 [`inotify(7)`]: https://man7.org/linux/man-pages/man7/inotify.7.html
 [`kqueue(2)`]: https://www.freebsd.org/cgi/man.cgi?query=kqueue&sektion=2
 [`minimatch`]: https://github.com/isaacs/minimatch