fix(extensions): render hyphenated hook invocations for Forge projects (#3641)

Forge is a hyphenated slash-command agent: it registers its commands as
`/speckit-<name>` (see `format_forge_command_name` and
`ForgeIntegration.build_command_invocation`), exactly like Cline.

`HookExecutor._render_hook_invocation` special-cases dollar-skills agents,
kimi, cline, and slash-skills agents, but had no Forge branch. Forge
matches none of those, so it fell through to `return f"/{command_id}"`
and rendered the DOTTED form — `/speckit.plan`, `/speckit.git.commit` —
which Forge does not recognize as a registered command.

Add a Forge branch mirroring the adjacent Cline branch, using
`format_forge_command_name` (idempotent, same contract as the Cline
formatter). Non-Forge agents are unaffected.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/specify_cli/extensions/__init__.py

@@ -3608,6 +3608,7 @@ class HookExecutor:
         dollar_skill_mode = is_dollar_skills_agent(selected_ai, ai_skills_enabled)
         kimi_skill_mode = selected_ai == "kimi"
         cline_mode = selected_ai == "cline"
+        forge_mode = selected_ai == "forge"
 
         skill_name = self._skill_name_from_command(command_id)
         if dollar_skill_mode and skill_name:
@@ -3618,6 +3619,10 @@ class HookExecutor:
             from ..integrations.cline import format_cline_command_name
 
             return f"/{format_cline_command_name(command_id)}"
+        if forge_mode:
+            from ..integrations.forge import format_forge_command_name
+
+            return f"/{format_forge_command_name(command_id)}"
 
         use_slash = is_slash_skills_agent(selected_ai, ai_skills_enabled)