Add Help component for CLI usage and input validation support

- Introduced `Help` class for generating CLI help/usage blocks with options, descriptions, and customizable formatting.
- Enhanced `Prompt` and `PromptBuilder` with validation capabilities using predicates and retry messages.
- Added terminal control methods `clearScreen` and `cursorTo` with ANSI support.
- Updated examples and documentation (`Examples.md`, `Components.md`) to showcase the new features.
- Extended `Examples` class with a `helpBlock` method for demonstrating the `Help` usage.

docs/Components.md

@@ -26,11 +26,12 @@ Overview of what terminal-ui provides. All entry points are on `Terminal.*`.
 
 | API | Description |
 |-----|-------------|
-| `Terminal.prompt(String)` | Text input (`.ask()`, `.masked().ask()`) |
+| `Terminal.prompt(String)` | Text input (`.ask()`, `.masked().ask()`, `.validate(Predicate).retryMessage(String)`) |
 | `Terminal.confirm(String)` | Y/n confirmation |
 | `Terminal.menu()` | Numbered menu (`.option()`, `.select()`) |
 | `Terminal.selectList()` | List with arrow keys + Enter |
 | `Terminal.pager()` | Paged output (Enter/arrows/q) |
+| `Terminal.help()` | CLI usage block (`.option(opt, desc)`, `.title()`) |
 
 ## Live / progress
 
@@ -50,6 +51,13 @@ Overview of what terminal-ui provides. All entry points are on `Terminal.*`.
 | `Terminal.heatmap()` | Heatmap |
 | `Terminal.chart()` | Charts |
 
+## Terminal control (ANSI)
+
+| API | Description |
+|-----|-------------|
+| `Terminal.clearScreen()` | Clear entire screen |
+| `Terminal.cursorTo(row, col)` | Move cursor (1-based) |
+
 ## Other
 
 | API | Description |

docs/Examples.md

@@ -108,6 +108,13 @@ String name = Terminal.prompt("Name: ").ask();
 String secret = Terminal.prompt("Password: ").masked().ask();
 // With shared scanner (e.g. in a loop):
 String line = Terminal.prompt("Input: ").ask(sharedScanner);
+
+// With validation (asks again until input matches):
+String age = Terminal.prompt("Age: ").validate(s -> s.matches("\\d+")).ask();
+String email = Terminal.prompt("Email: ")
+    .validate(s -> s.contains("@"))
+    .retryMessage("Invalid email, try again: ")
+    .ask();
 ```
 
 ## Interactive: Confirm
@@ -259,6 +266,26 @@ Terminal.code("java")
     .print(System.out);
 ```
 
+## Help (CLI usage)
+
+```java
+Terminal.help()
+    .title("Options")
+    .option("-v, --verbose", "Enable verbose output")
+    .option("-h, --help", "Show this help")
+    .option("--file <path>", "Input file path")
+    .print(System.out);
+```
+
+## Clear screen & cursor
+
+```java
+Terminal.clearScreen();       // Clear terminal (ANSI)
+Terminal.cursorTo(1, 1);      // Move cursor to row 1, col 1 (1-based)
+```
+
+No-op when ANSI is disabled.
+
 ## SysInfo
 
 ```java