Update cp docs: permissions preserved by default

docs/cli/manage-your-fleet.md

@@ -114,7 +114,8 @@ Copy a directory recursively:
 viam machines part cp --part=<part-id> -r ./local-dir machine:/home/user/
 ```
 
-Preserve file permissions and timestamps:
+File permissions are preserved by default, matching `scp` behavior.
+Use `--preserve` to also keep modification timestamps and force exact permission bits (bypassing umask):
 
 ```sh {class="command-line" data-prompt="$"}
 viam machines part cp --part=<part-id> -r --preserve ./local-dir machine:/home/user/

docs/cli/reference.md

@@ -1260,7 +1260,7 @@ viam machines part cp --part=123 my_file machine:/home/user/
 # Recursively copy a directory to a machine:
 viam machines part cp --part=123 -r my_dir machine:/home/user/
 
-# Copy multiple files to a machine with recursion and keep original permissions and metadata for the files:
+# Copy multiple files to a machine with recursion and preserve exact permissions and timestamps:
 viam machines part cp --part=123 -r -p my_dir my_file machine:/home/user/some/existing/dir/
 
 # Copy a single file from a machine to a local destination:
@@ -1269,7 +1269,7 @@ viam machines part cp --part=123 machine:my_file ~/Downloads/
 # Recursively copy a directory from a machine to a local destination:
 viam machines part cp --part=123 -r machine:my_dir ~/Downloads/
 
-# Copy multiple files from the machine to a local destination with recursion and keep original permissions and metadata for the files:
+# Copy multiple files from the machine to a local destination with recursion and preserve exact permissions and timestamps:
 viam machines part cp --part=123 -r -p machine:my_dir machine:my_file ~/some/existing/dir/
 ```
 
@@ -1278,7 +1278,7 @@ viam machines part cp --part=123 -r -p machine:my_dir machine:my_file ~/some/exi
 | -------- | ----------- | --------- |
 | `--part` | Part ID for which the command is being issued. | **Required** |
 | `--recursive`, `-r` | Recursively copy files. Default: `false`. | Optional |
-| `--preserve`, `-p` | Preserve modification times and file mode bits from the source files. Default: `false`. | Optional |
+| `--preserve`, `-p` | Preserve modification times and set exact file permissions from the source, bypassing umask. File permissions are always transferred by default; this flag additionally preserves timestamps and forces exact permission bits. Default: `false`. | Optional |
 
 ### `machines part tunnel`