feat: Add runtime configuration help system

Implement CONFIG HELP, CONFIG SHOW, and CONFIG VERIFY commands to provide
runtime configuration guidance without external documentation.

Changes:
- Add ConfigSchemaExplorer to navigate JSON Schema and extract help info
- Implement CONFIG HELP [path] - display help for config options
- Implement CONFIG SHOW [path] - display current config (masks secrets)
- Implement CONFIG VERIFY <filepath> - validate config files
- Add sensitive field masking (password, secret, key, token)
- Update QueryParser to support CONFIG subcommands
- Extend AdminHandler with CONFIG command handlers
- Add comprehensive tests (41 tests: 22 unit + 19 integration)
- Update documentation (en/ja for protocol and configuration)

Features:
- Runtime config exploration via dot-separated paths (e.g., mysql.port)
- Automatic masking of sensitive fields with ***
- Schema-based help with types, defaults, ranges, descriptions
- Config file verification without loading into running server

Closes #4

Author: libraz

docs/en/configuration.md

@@ -522,6 +522,96 @@ MygramDB automatically validates all configuration files (YAML and JSON) using a
 
 If validation fails, MygramDB will display a detailed error message pointing to the exact problem.
 
+## Runtime Configuration Help
+
+MygramDB provides runtime commands to explore configuration options, view current settings, and verify configuration files without restarting the server.
+
+### Getting Configuration Help
+
+You can query configuration help at runtime using the `CONFIG HELP` command:
+
+```bash
+# Show all configuration sections
+echo "CONFIG HELP" | nc localhost 11016
+```
+
+**Example output:**
+```
++OK
+Available configuration sections:
+  mysql        - MySQL connection settings
+  tables       - Table configuration (supports multiple tables)
+  build        - Index build configuration
+  replication  - Replication configuration
+  memory       - Memory management
+  ...
+```
+
+### Viewing Detailed Help
+
+Get help for specific configuration options:
+
+```bash
+# Help for MySQL section
+echo "CONFIG HELP mysql" | nc localhost 11016
+
+# Help for a specific property
+echo "CONFIG HELP mysql.port" | nc localhost 11016
+```
+
+This displays:
+- Property type (string, integer, boolean, etc.)
+- Default value
+- Valid range or allowed values
+- Description
+- Whether the field is required
+
+### Viewing Current Configuration
+
+View the running configuration with sensitive fields masked:
+
+```bash
+# Show entire configuration
+echo "CONFIG SHOW" | nc localhost 11016
+
+# Show specific section
+echo "CONFIG SHOW mysql" | nc localhost 11016
+
+# Show specific property
+echo "CONFIG SHOW mysql.port" | nc localhost 11016
+```
+
+**Note**: Sensitive fields (passwords, secrets, keys, tokens) are automatically masked as `***` in the output.
+
+### Verifying Configuration Files
+
+Verify a configuration file before deploying it:
+
+```bash
+echo "CONFIG VERIFY /path/to/config.yaml" | nc localhost 11016
+```
+
+This validates the configuration without loading it into the running server. If the configuration is valid, you'll see a summary:
+
+```
++OK
+Configuration is valid
+  Tables: 2 (articles, products)
+  MySQL: repl_user@127.0.0.1:3306
+```
+
+If invalid, you'll see detailed error messages:
+
+```
+-ERR Configuration validation failed:
+  - mysql.port: value 99999 exceeds maximum 65535
+  - tables[0].name: missing required field
+```
+
+For complete CONFIG command syntax, see the [Protocol Reference](protocol.md#config-commands).
+
+---
+
 ## Testing Configuration
 
 Before starting the server, you can test your configuration file:

docs/en/protocol.md

@@ -185,27 +185,208 @@ replication_deletes_applied: 5000
 
 ---
 
-## CONFIG Command
+## CONFIG Commands
 
-Get current server configuration (all settings).
+The CONFIG command family provides runtime configuration help, inspection, and verification.
 
-### Syntax
+### CONFIG HELP [path]
+
+Display help for configuration options.
 
+**Syntax:**
 ```
-CONFIG
+CONFIG HELP [path]
 ```
 
-### Response
+**Parameters:**
+- `path` (optional): Dot-separated configuration path (e.g., `mysql.port`)
+
+**Examples:**
+
+Show all top-level configuration sections:
+```
+CONFIG HELP
+```
+
+Response:
+```
++OK
+Available configuration sections:
+  mysql        - MySQL connection settings
+  tables       - Table configuration (supports multiple tables)
+  build        - Index build configuration
+  replication  - Replication configuration
+  memory       - Memory management
+  dump         - Dump persistence (automatic backup)
+  api          - API server configuration
+  network      - Network security (optional)
+  logging      - Logging configuration
+  cache        - Query cache configuration
+
+Use "CONFIG HELP <section>" for detailed information.
+```
+
+Show help for a specific section:
+```
+CONFIG HELP mysql
+```
+
+Response:
+```
++OK
+mysql - MySQL connection settings
+
+Properties:
+  host (string, default: "127.0.0.1")
+    MySQL server hostname or IP
+
+  port (integer, default: 3306, range: 1-65535)
+    MySQL server port
+
+  user (string, REQUIRED)
+    MySQL username for replication
+
+  password (string)
+    MySQL user password
+
+  database (string, REQUIRED)
+    Database name
+
+  use_gtid (boolean, default: true)
+    Enable GTID-based replication
+
+  ...
+```
+
+Show help for a specific property:
+```
+CONFIG HELP mysql.port
+```
+
+Response:
+```
++OK
+mysql.port
+
+Type: integer
+Default: 3306
+Range: 1 - 65535
+Description: MySQL server port
+```
+
+---
+
+### CONFIG SHOW [path]
+
+Display current configuration values. Sensitive fields (passwords, secrets) are masked with `***`.
+
+**Syntax:**
+```
+CONFIG SHOW [path]
+```
+
+**Parameters:**
+- `path` (optional): Dot-separated configuration path to show only specific section
+
+**Examples:**
 
-Returns a YAML-style formatted configuration showing:
-- MySQL connection settings
-- Table configurations (name, primary_key, ngram_size, filters count)
-- API server settings (bind address and port)
-- Replication settings (enable, server_id, start_from)
-- Memory configuration (limits, thresholds)
-- Snapshot directory
-- Logging level
-- Runtime status (connections, uptime, read_only mode)
+Show entire current configuration:
+```
+CONFIG SHOW
+```
+
+Response:
+```
++OK
+mysql:
+  host: "127.0.0.1"
+  port: 3306
+  user: "repl_user"
+  password: "***"
+  database: "mydb"
+  use_gtid: true
+  ...
+
+tables:
+  - name: "articles"
+    primary_key: "id"
+    ...
+
+replication:
+  enable: true
+  server_id: 12345
+  ...
+```
+
+Show specific section:
+```
+CONFIG SHOW mysql
+```
+
+Response:
+```
++OK
+mysql:
+  host: "127.0.0.1"
+  port: 3306
+  user: "repl_user"
+  password: "***"
+  database: "mydb"
+  use_gtid: true
+  ...
+```
+
+Show specific property:
+```
+CONFIG SHOW mysql.port
+```
+
+Response:
+```
++OK
+3306
+```
+
+---
+
+### CONFIG VERIFY <filepath>
+
+Verify a configuration file without loading it.
+
+**Syntax:**
+```
+CONFIG VERIFY <filepath>
+```
+
+**Parameters:**
+- `filepath` (required): Path to configuration file (YAML or JSON)
+
+**Examples:**
+
+Verify valid config:
+```
+CONFIG VERIFY /etc/mygramdb/config.yaml
+```
+
+Response (success):
+```
++OK
+Configuration is valid
+  Tables: 2 (articles, products)
+  MySQL: repl_user@127.0.0.1:3306
+```
+
+Verify invalid config:
+```
+CONFIG VERIFY /tmp/invalid.yaml
+```
+
+Response (error):
+```
+-ERR Configuration validation failed:
+  - mysql.port: value 99999 exceeds maximum 65535
+  - tables[0].name: missing required field
+```
 
 ---