feat: migrate Forge agent to Python integration system

- Create ForgeIntegration class with custom processing for {{parameters}}, handoffs stripping, and name injection
- Add update-context scripts (bash and PowerShell) for Forge
- Register Forge in integration registry
- Update AGENTS.md with Forge documentation and special processing requirements section
- Add comprehensive test suite (11 tests, all passing)

Closes migration from release packaging to Python-based scaffolding for Forge agent.

tests/integrations/test_integration_forge.py

@@ -0,0 +1,144 @@
+"""Tests for ForgeIntegration."""
+
+from specify_cli.integrations import get_integration
+from specify_cli.integrations.manifest import IntegrationManifest
+
+
+class TestForgeIntegration:
+    def test_forge_key_and_config(self):
+        forge = get_integration("forge")
+        assert forge is not None
+        assert forge.key == "forge"
+        assert forge.config["folder"] == ".forge/"
+        assert forge.config["commands_subdir"] == "commands"
+        assert forge.config["requires_cli"] is True
+        assert forge.registrar_config["args"] == "{{parameters}}"
+        assert forge.registrar_config["extension"] == ".md"
+        assert forge.context_file == "AGENTS.md"
+
+    def test_command_filename_md(self):
+        forge = get_integration("forge")
+        assert forge.command_filename("plan") == "speckit.plan.md"
+
+    def test_setup_creates_md_files(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        created = forge.setup(tmp_path, m)
+        assert len(created) > 0
+        # Separate command files from scripts
+        command_files = [f for f in created if f.parent == tmp_path / ".forge" / "commands"]
+        assert len(command_files) > 0
+        for f in command_files:
+            assert f.name.endswith(".md")
+
+    def test_setup_installs_update_scripts(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        created = forge.setup(tmp_path, m)
+        script_files = [f for f in created if "scripts" in f.parts]
+        assert len(script_files) > 0
+        sh_script = tmp_path / ".specify" / "integrations" / "forge" / "scripts" / "update-context.sh"
+        ps_script = tmp_path / ".specify" / "integrations" / "forge" / "scripts" / "update-context.ps1"
+        assert sh_script in created
+        assert ps_script in created
+        assert sh_script.exists()
+        assert ps_script.exists()
+
+    def test_all_created_files_tracked_in_manifest(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        created = forge.setup(tmp_path, m)
+        for f in created:
+            rel = f.resolve().relative_to(tmp_path.resolve()).as_posix()
+            assert rel in m.files, f"Created file {rel} not tracked in manifest"
+
+    def test_install_uninstall_roundtrip(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        created = forge.install(tmp_path, m)
+        assert len(created) > 0
+        m.save()
+        for f in created:
+            assert f.exists()
+        removed, skipped = forge.uninstall(tmp_path, m)
+        assert len(removed) == len(created)
+        assert skipped == []
+
+    def test_modified_file_survives_uninstall(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        created = forge.install(tmp_path, m)
+        m.save()
+        # Modify a command file (not a script)
+        command_files = [f for f in created if f.parent == tmp_path / ".forge" / "commands"]
+        modified_file = command_files[0]
+        modified_file.write_text("user modified this", encoding="utf-8")
+        removed, skipped = forge.uninstall(tmp_path, m)
+        assert modified_file.exists()
+        assert modified_file in skipped
+
+    def test_directory_structure(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        forge.setup(tmp_path, m)
+        commands_dir = tmp_path / ".forge" / "commands"
+        assert commands_dir.is_dir()
+        command_files = sorted(commands_dir.glob("speckit.*.md"))
+        assert len(command_files) == 9
+        expected_commands = {
+            "analyze", "checklist", "clarify", "constitution",
+            "implement", "plan", "specify", "tasks", "taskstoissues",
+        }
+        actual_commands = {f.name.removeprefix("speckit.").removesuffix(".md") for f in command_files}
+        assert actual_commands == expected_commands
+
+    def test_templates_are_processed(self, tmp_path):
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        forge.setup(tmp_path, m)
+        commands_dir = tmp_path / ".forge" / "commands"
+        for cmd_file in commands_dir.glob("speckit.*.md"):
+            content = cmd_file.read_text(encoding="utf-8")
+            # Check standard replacements
+            assert "{SCRIPT}" not in content, f"{cmd_file.name} has unprocessed {{SCRIPT}}"
+            assert "__AGENT__" not in content, f"{cmd_file.name} has unprocessed __AGENT__"
+            assert "{ARGS}" not in content, f"{cmd_file.name} has unprocessed {{ARGS}}"
+            # Note: $ARGUMENTS may appear in template content (examples, instructions)
+            # The placeholder that gets replaced is {ARGS}, not $ARGUMENTS
+            # Frontmatter sections should be stripped
+            assert "\nscripts:\n" not in content
+            assert "\nagent_scripts:\n" not in content
+
+    def test_forge_specific_transformations(self, tmp_path):
+        """Test Forge-specific processing: name injection and handoffs stripping."""
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        m = IntegrationManifest("forge", tmp_path)
+        forge.setup(tmp_path, m)
+        commands_dir = tmp_path / ".forge" / "commands"
+        
+        for cmd_file in commands_dir.glob("speckit.*.md"):
+            content = cmd_file.read_text(encoding="utf-8")
+            
+            # Check that name field is injected in frontmatter
+            assert "\nname: " in content, f"{cmd_file.name} missing injected 'name' field"
+            
+            # Check that handoffs frontmatter key is stripped
+            assert "\nhandoffs:" not in content, f"{cmd_file.name} has unstripped 'handoffs' key"
+
+    def test_uses_parameters_placeholder(self, tmp_path):
+        """Verify Forge config specifies {{parameters}} as the args placeholder."""
+        from specify_cli.integrations.forge import ForgeIntegration
+        forge = ForgeIntegration()
+        # The registrar_config should specify {{parameters}}
+        assert forge.registrar_config["args"] == "{{parameters}}"
+        
+        # When process_template is called, it should replace {ARGS} with {{parameters}}
+        # Note: $ARGUMENTS in template content is intentional (examples/instructions)