fix(integrations): escape control characters in SKILL.md frontmatter (#3399)

yaml.safe_dump with default_style='"' replaces the hand-rolled quote
helpers in base.py and hermes, so newlines and control characters in
template descriptions round-trip instead of producing unparseable YAML.

Fixes #3391

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/integrations/test_skill_frontmatter_quoting.py

@@ -0,0 +1,111 @@
+"""Regression tests for SKILL.md frontmatter quoting (#3391).
+
+The skills setup path builds SKILL.md frontmatter by hand with
+double-quoted values. A double-quoted YAML scalar cannot carry a raw
+newline (the parser folds it to a space) or a control character (the
+reader rejects the document), so descriptions taken from template
+frontmatter must be escaped by the YAML emitter.
+"""
+
+from pathlib import Path
+
+import yaml
+
+from specify_cli.integrations import get_integration
+from specify_cli.integrations.base import yaml_quote
+from specify_cli.integrations.manifest import IntegrationManifest
+
+MULTILINE = "first line\nsecond line\n"
+CONTROL = "ding\aling"
+
+HOSTILE_TEMPLATE = """---
+description: |
+  first line
+  second line
+---
+
+Body of the command.
+"""
+
+CONTROL_TEMPLATE = """---
+description: "ding\\aling"
+---
+
+Body of the command.
+"""
+
+
+def _parse_frontmatter(skill_file: Path) -> dict:
+    content = skill_file.read_text(encoding="utf-8")
+    assert content.startswith("---\n")
+    return yaml.safe_load(content.split("---", 2)[1])
+
+
+def _fake_templates(tmp_path: Path, body: str) -> Path:
+    templates = tmp_path / "templates"
+    templates.mkdir(exist_ok=True)
+    (templates / "plan.md").write_text(body, encoding="utf-8")
+    return templates
+
+
+class TestYamlQuote:
+    def test_simple_value_keeps_plain_double_quoted_form(self):
+        assert yaml_quote("speckit-plan") == '"speckit-plan"'
+        assert yaml_quote('say "hi"') == '"say \\"hi\\""'
+        assert yaml_quote("back\\slash") == '"back\\\\slash"'
+
+    def test_multiline_value_round_trips(self):
+        quoted = yaml_quote(MULTILINE)
+        assert "\n" not in quoted
+        assert yaml.safe_load(quoted) == MULTILINE
+
+    def test_control_character_round_trips(self):
+        quoted = yaml_quote(CONTROL)
+        assert "\a" not in quoted
+        assert yaml.safe_load(quoted) == CONTROL
+
+
+class TestSkillFrontmatterQuoting:
+    def _generate(self, tmp_path, monkeypatch, template: str) -> Path:
+        integration = get_integration("agy")
+        monkeypatch.setattr(
+            integration,
+            "shared_commands_dir",
+            lambda: _fake_templates(tmp_path, template),
+        )
+        manifest = IntegrationManifest("agy", tmp_path)
+        created = integration.setup(tmp_path, manifest)
+        skill_files = [f for f in created if f.name == "SKILL.md"]
+        assert len(skill_files) == 1
+        return skill_files[0]
+
+    def test_multiline_description_survives(self, tmp_path, monkeypatch):
+        skill_file = self._generate(tmp_path, monkeypatch, HOSTILE_TEMPLATE)
+        fm = _parse_frontmatter(skill_file)
+        assert fm["description"] == MULTILINE
+
+    def test_control_character_description_parses(self, tmp_path, monkeypatch):
+        skill_file = self._generate(tmp_path, monkeypatch, CONTROL_TEMPLATE)
+        fm = _parse_frontmatter(skill_file)
+        assert fm["description"] == CONTROL
+
+
+class TestHermesSkillFrontmatterQuoting:
+    def test_multiline_description_survives(self, tmp_path, monkeypatch):
+        home = tmp_path / "home"
+        home.mkdir(exist_ok=True)
+        monkeypatch.setattr(Path, "home", lambda: home)
+
+        integration = get_integration("hermes")
+        monkeypatch.setattr(
+            integration,
+            "shared_commands_dir",
+            lambda: _fake_templates(tmp_path, HOSTILE_TEMPLATE),
+        )
+        manifest = IntegrationManifest("hermes", tmp_path)
+        created = integration.setup(tmp_path, manifest)
+        skill_files = [f for f in created if f.name == "SKILL.md"]
+        assert len(skill_files) == 1
+
+        fm = _parse_frontmatter(skill_files[0])
+        assert fm["description"] == MULTILINE