docs(plugins): correct keystore CLI option names in README

Two CLI flags in plugins/README.md did not match the actual @option
declarations in the picocli command classes — users following the docs
verbatim would hit "Unknown option" errors:

- `keystore import` was documented with `--private-key-file`, but the
  actual option in KeystoreImport.java:41 is `--key-file`. Updated the
  full-command synopsis and the example accordingly, and added the
  missing `--force` flag (used by the duplicate-address override path).

- `keystore update` was documented with a separate `--new-password-file`,
  but KeystoreUpdate.java only defines a single `--password-file` whose
  contents are a two-line file (current password, then new password).
  Removed the bogus flag and added an explicit note next to the synopsis
  describing the expected file format, plus an updated entry in the
  Common Options list.

No code changes — purely documentation alignment so the README matches
the implemented CLI surface.

Author: Barbatos

plugins/README.md

@@ -175,10 +175,10 @@ Import a private key into a new keystore file.
 
 ```shell script
 # full command
-  java -jar Toolkit.jar keystore import [-h] [--keystore-dir=<dir>] [--password-file=<file>] [--private-key-file=<file>] [--sm2] [--json]
+  java -jar Toolkit.jar keystore import [-h] [--keystore-dir=<dir>] [--password-file=<file>] [--key-file=<file>] [--sm2] [--force] [--json]
 # examples
-  java -jar Toolkit.jar keystore import                                        # interactive prompt
-  java -jar Toolkit.jar keystore import --private-key-file key.txt --json      # from file with JSON output
+  java -jar Toolkit.jar keystore import                                # interactive prompt
+  java -jar Toolkit.jar keystore import --key-file key.txt --json      # from file with JSON output
 ```
 
 #### keystore list
@@ -201,16 +201,20 @@ Change the password of a keystore file.
 
 ```shell script
 # full command
-  java -jar Toolkit.jar keystore update [-h] <address> [--keystore-dir=<dir>] [--password-file=<file>] [--new-password-file=<file>] [--json]
+  java -jar Toolkit.jar keystore update [-h] <address> [--keystore-dir=<dir>] [--password-file=<file>] [--sm2] [--json]
 # examples
   java -jar Toolkit.jar keystore update TXyz...abc                          # interactive prompt
   java -jar Toolkit.jar keystore update TXyz...abc --keystore-dir /data/ks  # custom directory
 ```
 
+When using `--password-file` with `update`, the file must contain exactly two lines: the **current** password on the first line and the **new** password on the second line. Both leading/trailing whitespace within a line is preserved (passphrases with spaces are supported).
+
 ### Common Options
 
 - `--keystore-dir`: Keystore directory, default: `./Wallet`.
-- `--password-file`: Read password from a file instead of interactive prompt.
+- `--password-file`: Read password from a file instead of interactive prompt. For `keystore update`, the file must contain exactly two lines (current password, then new password).
+- `--key-file`: Read the private key (hex, with or without `0x` prefix) from a file instead of the interactive prompt (`keystore import` only).
+- `--force`: For `keystore import`, allow importing a private key whose address already has a keystore in the directory (creates an additional file).
 - `--sm2`: Use SM2 algorithm instead of ECDSA (for `new` and `import`).
 - `--json`: Output in JSON format for scripting.
 - `-h | --help`: Provide the help info.