Refactor unlockers command structure and add quiet flag to list command

- Rename 'unlockers' command to 'unlocker' for consistency
- Move all unlocker subcommands (list, add, remove) under single 'unlocker' command
- Add --quiet/-q flag to 'secret list' for scripting support
- Update documentation and tests to reflect command changes

The quiet flag outputs only secret names without headers or formatting,
making it ideal for shell script usage like: secret get $(secret list -q | head -1)

README.md

@@ -132,10 +132,10 @@ Generates and stores a random secret.
 
 ### Unlocker Management
 
-#### `secret unlockers list [--json]` / `secret unlockers ls`
+#### `secret unlocker list [--json]` / `secret unlocker ls`
 Lists all unlockers in the current vault with their metadata.
 
-#### `secret unlockers add <type> [options]`
+#### `secret unlocker add <type> [options]`
 Creates a new unlocker of the specified type:
 
 **Types:**
@@ -146,7 +146,7 @@ Creates a new unlocker of the specified type:
 **Options:**
 - `--keyid <id>`: GPG key ID (required for PGP type)
 
-#### `secret unlockers remove <unlocker-id> [--force]` / `secret unlockers rm` ⚠️ 🛑
+#### `secret unlocker remove <unlocker-id> [--force]` / `secret unlocker rm` ⚠️ 🛑
 **DANGER**: Permanently removes an unlocker. Like Unix `rm`, this command does not ask for confirmation.
 Cannot remove the last unlocker if the vault has secrets unless --force is used.
 - `--force, -f`: Force removal of last unlocker even if vault has secrets
@@ -308,7 +308,7 @@ secret vault create personal
 # Work with work vault
 secret vault select work
 echo "work-db-pass" | secret add database/password
-secret unlockers add passphrase  # Add passphrase authentication
+secret unlocker add passphrase  # Add passphrase authentication
 
 # Switch to personal vault
 secret vault select personal
@@ -324,18 +324,18 @@ secret vault remove personal --force
 ### Advanced Authentication
 ```bash
 # Add multiple unlock methods
-secret unlockers add passphrase              # Password-based
-secret unlockers add pgp --keyid ABCD1234    # GPG key
-secret unlockers add keychain                # macOS Keychain (macOS only)
+secret unlocker add passphrase              # Password-based
+secret unlocker add pgp --keyid ABCD1234    # GPG key
+secret unlocker add keychain                # macOS Keychain (macOS only)
 
 # List unlockers
-secret unlockers list
+secret unlocker list
 
 # Select a specific unlocker
 secret unlocker select <unlocker-id>
 
 # Remove an unlocker ⚠️ 🛑 (NO CONFIRMATION!)
-secret unlockers remove <unlocker-id>
+secret unlocker remove <unlocker-id>
 ```
 
 ### Version Management