fix(integrations): Forge dispatches hyphenated /speckit-<cmd> invocations (#3529)

Forge installs its slash-commands with hyphenated names (speckit-foo-bar, via
format_forge_command_name and the injected frontmatter name), but
ForgeIntegration inherited MarkdownIntegration.build_command_invocation, which
builds the dotted /speckit.<cmd>. So 'workflow'/command dispatch invoked
/speckit.plan while the registered command is /speckit-plan — a name Forge never
registered.

Override build_command_invocation to reuse format_forge_command_name, producing
/speckit-<name> (with '.'-to-'-' for extension commands), mirroring the skills
agents' hyphenated invocation.

Tests assert Forge core + extension invocations are hyphenated, incl. args
(fail before: dotted /speckit.plan / /speckit.git.commit).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/specify_cli/integrations/forge/__init__.py

@@ -91,6 +91,18 @@ class ForgeIntegration(MarkdownIntegration):
     }
     invoke_separator = "-"
 
+    def build_command_invocation(self, command_name: str, args: str = "") -> str:
+        """Forge installs hyphenated slash-commands (``/speckit-<name>``), so the
+        dispatch invocation must match. The inherited MarkdownIntegration default
+        builds the dotted ``/speckit.<name>``, which references a command Forge
+        never registered. Reuse the same hyphenation as the installed frontmatter
+        ``name`` (see ``format_forge_command_name``), mirroring the skills agents.
+        """
+        invocation = "/" + format_forge_command_name(command_name)
+        if args:
+            invocation = f"{invocation} {args}"
+        return invocation
+
     def setup(
         self,
         project_root: Path,