feat: Default to union operator for type hints (#2703)

* feat: Replace Optional with Union type hints for improved type clarity

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Update type hints to use Optional and Union for better compatibility

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Enhance type hinting by replacing Optional with Union and adding support for native union types

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Enhance type hinting by replacing Optional with Union and adding support for native union types

* feat: Refactor type hint handling to improve union type hint generation

* feat: Update type hints to use native union types and improve readability

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Update type hints to use native union types across multiple files

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Add LEGACY_BLACK_SKIP decorator to JSON Schema test functions

* feat: Add LEGACY_BLACK_SKIP decorator to JSON Schema test functions

* feat: Apply LEGACY_BLACK_SKIP decorator to relevant test functions

* feat: Apply LEGACY_BLACK_SKIP decorator to relevant test functions

* feat: Add coverage pragma to type hint method return

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: koxudaxi

docs/cli-reference/base-options.md

@@ -62,14 +62,12 @@ For consistent cross-platform behavior, explicitly specify `--encoding utf-8`.
 
     from __future__ import annotations
 
-    from typing import Optional
-    
     from pydantic import BaseModel, Field
 
 
     class 日本語Model(BaseModel):
-        名前: Optional[str] = Field(None, description='ユーザー名')
-        年齢: Optional[int] = None
+        名前: str | None = Field(None, description='ユーザー名')
+        年齢: int | None = None
     ```
 
 ---
@@ -122,15 +120,13 @@ schemas. Required unless using `--url` to fetch schema from a URL.
 
     from __future__ import annotations
 
-    from typing import Optional
-    
     from pydantic import BaseModel
 
 
     class Pet(BaseModel):
-        id: Optional[int] = None
-        name: Optional[str] = None
-        tag: Optional[str] = None
+        id: int | None = None
+        name: str | None = None
+        tag: str | None = None
     ```
 
 ---
@@ -236,15 +232,13 @@ is written to stdout.
 
     from __future__ import annotations
 
-    from typing import Optional
-    
     from pydantic import BaseModel
 
 
     class Pet(BaseModel):
-        id: Optional[int] = None
-        name: Optional[str] = None
-        tag: Optional[str] = None
+        id: int | None = None
+        name: str | None = None
+        tag: str | None = None
     ```
 
 ---
@@ -298,15 +292,13 @@ Format: `HeaderName:HeaderValue`.
 
     from __future__ import annotations
 
-    from typing import Optional
-    
     from pydantic import BaseModel
 
 
     class Pet(BaseModel):
-        id: Optional[int] = None
-        name: Optional[str] = None
-        tag: Optional[str] = None
+        id: int | None = None
+        name: str | None = None
+        tag: str | None = None
     ```
 
 ---