feat(init): deprecate --no-git flag, gate deprecations at v0.10.0 (#2357)

* feat(init): deprecate --no-git flag, gate deprecations at v0.10.0

- Add deprecation warning when --no-git is used on specify init
- Update --ai deprecation gate from 1.0.0 to 0.10.0
- Update test expectation for the new version gate

Closes #2167

* fix: address PR review feedback

- Update --no-git deprecation message to reference existing 'specify extension'
  commands instead of non-existent --extension flag
- Add test_no_git_emits_deprecation_warning CLI test

* fix: strengthen --no-git deprecation test assertions

Add assertions unique to the --no-git message ('will be removed',
'git extension will no longer be enabled by default') to prevent
false positives from the --ai deprecation panel.

src/specify_cli/__init__.py

@@ -127,7 +127,7 @@ def _build_ai_deprecation_warning(
         ai_commands_dir=ai_commands_dir,
     )
     return (
-        "[bold]--ai[/bold] is deprecated and will no longer be available in version 1.0.0 or later.\n\n"
+        "[bold]--ai[/bold] is deprecated and will no longer be available in version 0.10.0 or later.\n\n"
         f"Use [bold]{replacement}[/bold] instead."
     )
 
@@ -1088,6 +1088,13 @@ def init(
                 'use [bold]--integration generic --integration-options="--commands-dir <dir>"[/bold] instead.[/dim]'
             )
 
+    if no_git:
+        console.print(
+            "[yellow]⚠️  --no-git is deprecated and will be removed in v0.10.0.[/yellow]\n"
+            "[yellow]The git extension will no longer be enabled by default "
+            "— use the [bold]specify extension[/bold] commands to install or enable the git extension if needed.[/yellow]"
+        )
+
     if project_name == ".":
         here = True
         project_name = None  # Clear project_name to use existing validation logic