fix: update JSON fields from snake_case to camelCase and make tests quiet by default

- Update all JSON field references in tests from snake_case to camelCase
- Update vault list JSON output to use currentVault instead of current_vault
- Make integration tests quiet by default unless run with -v flag
- Fix tests that were using exec.Command to use in-process execution helpers
- Tests now only show debug output when explicitly requested or on failure

internal/secret/pgpunlock_test.go

@@ -357,9 +357,9 @@ Passphrase: ` + testPassphrase + `
 		var metadata struct {
 			ID        string    `json:"id"`
 			Type      string    `json:"type"`
-			CreatedAt time.Time `json:"created_at"`
+			CreatedAt time.Time `json:"createdAt"`
 			Flags     []string  `json:"flags"`
-			GPGKeyID  string    `json:"gpg_key_id"`
+			GPGKeyID  string    `json:"gpgKeyId"`
 		}
 
 		if err := json.Unmarshal(metadataBytes, &metadata); err != nil {
@@ -396,7 +396,7 @@ Passphrase: ` + testPassphrase + `
 		// Create PGP metadata with GPG key ID
 		type PGPUnlockerMetadata struct {
 			secret.UnlockerMetadata
-			GPGKeyID string `json:"gpg_key_id"`
+			GPGKeyID string `json:"gpgKeyId"`
 		}
 
 		pgpMetadata := PGPUnlockerMetadata{