fix(init): show hyphenated /speckit-<name> in Next Steps for Forge projects (#3642)

The post-init "Next Steps" panel renders recommended slash commands via
the nested `_display_cmd()`. It special-cased dollar-skills agents, kimi,
slash-skills agents, and cline, but not Forge. For a Forge project
`_display_cmd` fell through to `return f"/speckit.{name}"`, printing
`/speckit.constitution`, `/speckit.specify`, etc.

Forge only registers the hyphenated form (`/speckit-<name>`, per
`format_forge_command_name` / `ForgeIntegration.build_command_invocation`,
and the generated command-file tests already assert this), so the panel
told Forge users to run commands that don't exist under the dotted name.

Add `forge_skill_mode` alongside `cline_skill_mode` and include it in the
hyphenated-slash condition, mirroring how cline (also a non-skills
markdown agent with hyphenated commands) is handled. Other agents
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/commands/init.py

@@ -700,6 +700,7 @@ def register(app: typer.Typer) -> None:
         zed_skill_mode = selected_ai == "zed" and _is_skills_integration
         grok_skill_mode = selected_ai == "grok" and _is_skills_integration
         cline_skill_mode = selected_ai == "cline"
+        forge_skill_mode = selected_ai == "forge"
         bob_skill_mode = selected_ai == "bob" and _is_skills_integration
         native_skill_mode = (
             codex_skill_mode
@@ -776,6 +777,7 @@ def register(app: typer.Typer) -> None:
             if (
                 _is_slash_skills_agent(selected_ai, _ai_skills_enabled)
                 or cline_skill_mode
+                or forge_skill_mode
             ):
                 return f"/speckit-{name}"
             return f"/speckit.{name}"