feat: Add SYNC command for manual table synchronization

Add SYNC and SYNC_STATUS commands to allow manual triggering of table
synchronization from MySQL binlog. This addresses the need for on-demand
synchronization without relying solely on automatic replication.

Changes:
- Add SyncHandler for SYNC and SYNC_STATUS commands
- Add sync state tracking (IN_PROGRESS, COMPLETED, FAILED)
- Add syncing_tables set to prevent concurrent syncs
- Update query parser to support SYNC commands
- Add comprehensive tests for sync functionality
- Add documentation for SYNC command usage
- Fix clang-tidy warnings:
  - Add NOLINT comments for intentional reference members
  - Fix else-after-return in sync handler
  - Replace magic number with named constant
  - Add explicit static_cast for narrowing conversions
  - Add deleted copy/move for RAII guard
  - Use explicit nullptr comparison

Closes #2

Author: libraz

docs/en/configuration.md

@@ -51,6 +51,7 @@ build:
 
 replication:
   enable: true
+  auto_initial_snapshot: false
   server_id: 12345
   start_from: "snapshot"
   queue_size: 10000
@@ -326,6 +327,11 @@ Index build configuration:
 MySQL binlog replication settings:
 
 - **enable**: Enable binlog replication (default: `true`)
+- **auto_initial_snapshot**: Automatically build snapshot on startup (default: `false`)
+  - `false`: Manual snapshot synchronization using `SYNC` command (recommended, safe by default)
+  - `true`: Legacy behavior - automatically build snapshot on startup
+  - Setting to `false` prevents unexpected MySQL load on startup
+  - See [SYNC Command Guide](sync_command.md) for manual synchronization
 - **server_id**: MySQL server ID (required, must be non-zero and unique in replication topology)
   - Generate a random number or use a unique value for your environment
   - Example: `12345`

docs/en/protocol.md

@@ -41,7 +41,7 @@ SEARCH articles hello
 
 With filters and pagination:
 ```
-SEARCH articles tech FILTER status=1 LIMIT 10
+SEARCH articles tech FILTER status = 1 LIMIT 10
 ```
 
 ### Response
@@ -67,7 +67,7 @@ COUNT <table> <text> [OPTIONS]
 ### Example
 
 ```
-COUNT articles tech AND AI FILTER status=1
+COUNT articles tech AND AI FILTER status = 1
 ```
 
 ### Response
@@ -209,40 +209,6 @@ Returns a YAML-style formatted configuration showing:
 
 ---
 
-## CONFIG VERIFY
-
-Validate current configuration and check system status.
-
-### Syntax
-
-```
-CONFIG VERIFY
-```
-
-### Response
-
-```
-OK CONFIG VERIFIED
-tables: <count>
-
-table: <table_name>
-  primary_key: <column>
-  text_source: <source>
-  ngram_size: <size>
-  filters: <count>
-  required_filters: <count>
-  status: loaded|not_loaded
-  documents: <count>
-  terms: <count>
-
-replication:
-  status: running|stopped
-  gtid: <gtid>
-
-END
-```
-
----
 
 ## DUMP Commands
 
@@ -254,12 +220,12 @@ Save complete snapshot to single binary file (`.dmp`).
 
 **Syntax:**
 ```
-DUMP SAVE [<filepath>] [WITH STATISTICS]
+DUMP SAVE [<filepath>] [--with-stats]
 ```
 
 **Example:**
 ```
-DUMP SAVE /backup/mygramdb.dmp WITH STATISTICS
+DUMP SAVE /backup/mygramdb.dmp --with-stats
 ```
 
 ### DUMP LOAD
@@ -367,6 +333,123 @@ OK REPLICATION STARTED
 
 ---
 
+## SYNC
+
+Manually trigger snapshot synchronization from MySQL to MygramDB for a specific table.
+
+### Syntax
+
+```
+SYNC <table_name>
+```
+
+### Parameters
+
+- **table_name**: Name of the table to synchronize (must be configured in config file)
+
+### Response (Success)
+
+```
+OK SYNC STARTED table=<table_name> job_id=1
+```
+
+### Response (Error)
+
+```
+ERROR SYNC already in progress for table '<table_name>'
+ERROR Memory critically low. Cannot start SYNC. Check system memory.
+ERROR Table '<table_name>' not found in configuration
+```
+
+### Behavior
+
+- Runs asynchronously in the background
+- Returns immediately after starting
+- Builds snapshot from MySQL using SELECT query
+- Captures GTID at snapshot time
+- Automatically starts binlog replication with captured GTID when complete
+
+### Conflicts
+
+- **DUMP LOAD**: Blocked during SYNC (prevents data corruption)
+- **REPLICATION START**: Blocked during SYNC (SYNC auto-starts replication)
+- **SYNC** (same table): Blocked if already in progress
+
+### Example
+
+```bash
+# Using CLI
+mygram-cli SYNC articles
+
+# Using telnet
+echo "SYNC articles" | nc localhost 11016
+```
+
+---
+
+## SYNC STATUS
+
+Check the progress and status of SYNC operations.
+
+### Syntax
+
+```
+SYNC STATUS
+```
+
+### Response Examples
+
+**In Progress:**
+```
+table=articles status=IN_PROGRESS progress=10000/25000 rows (40.0%) rate=5000 rows/s
+```
+
+**Completed:**
+```
+table=articles status=COMPLETED rows=25000 time=5.2s gtid=uuid:123 replication=STARTED
+```
+
+**Failed:**
+```
+table=articles status=FAILED rows=5000 error="MySQL connection lost"
+```
+
+**Idle:**
+```
+status=IDLE message="No sync operation performed"
+```
+
+### Status Fields
+
+| Field | Description |
+|-------|-------------|
+| `table` | Table name being synced |
+| `status` | `IN_PROGRESS`, `COMPLETED`, `FAILED`, `IDLE`, `CANCELLED` |
+| `progress` | Current/total rows processed |
+| `rate` | Processing rate (rows/s) |
+| `rows` | Total rows processed |
+| `time` | Total processing time |
+| `gtid` | Captured snapshot GTID |
+| `replication` | Replication status: `STARTED`, `ALREADY_RUNNING`, `DISABLED`, `FAILED` |
+| `error` | Error message (if failed) |
+
+### Example
+
+```bash
+# Using CLI
+mygram-cli SYNC STATUS
+
+# Using telnet
+echo "SYNC STATUS" | nc localhost 11016
+```
+
+### See Also
+
+- [SYNC Command Guide](sync_command.md) - Detailed usage guide
+- [Replication Guide](replication.md) - Manual snapshot synchronization setup
+
+---
+
 ## OPTIMIZE Command
 
 Optimize index posting lists (convert Delta Encoding to Roaring Bitmap based on density).
@@ -567,7 +650,7 @@ In interactive mode, type `help` to see available commands:
 > help
 Available commands:
   SEARCH, COUNT, GET              - Search and retrieval
-  INFO, CONFIG, CONFIG VERIFY     - Server information and validation
+  INFO, CONFIG                    - Server information and configuration
   DUMP SAVE/LOAD/VERIFY/INFO      - Snapshot management
   REPLICATION STATUS/STOP/START   - Replication control
   OPTIMIZE                        - Index optimization