Add community node protocol spec, Agent Skills, and make the failing tests hermetic

Community nodes (Phase 1 of plan.md): the protocol specification in
services/nodes/spec.py as the single source of truth, GET /nodes/spec.json,
a generated protocol docs page, the Community nodes API docs group, and the
implementation plan plus the residential proxy research. The no-open-proxy rule
is enforced in the spec (open_proxy cannot be set).

Agent Skills: register the Skills API docs group, cascade skills on account
deletion, add the nested CLAUDE.md, README and routes docs, and cover the
parser, the fetcher (end to end against a mock origin), the data layer and the
routes with 73 unit and 16 api tests.

Tests made hermetic with the repo's existing patterns instead of ambient
environment: embeddings tests set OPENROUTER_API_KEY via monkeypatch, the
workspace tests install FakeBackend via runtime.set_backend, and the skills
install tests use run_async. DockerCliBackend now returns 127 (command not
found) when the CLI is missing instead of raising FileNotFoundError, so a host
without docker answers with a clean error rather than a 500. The Providers tab
empty state no longer names the Model routes tab.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/unit/services/skills/parser.py

@@ -0,0 +1,107 @@
+# retoor <retoor@molodetz.nl>
+
+import pytest
+
+from devplacepy.services.skills import limits
+from devplacepy.services.skills.parser import SkillFormatError, parse_skill_md
+
+
+def skill(frontmatter: str, body: str = "# Body\n\nDo the thing.") -> str:
+    return f"---\n{frontmatter}\n---\n{body}"
+
+
+def test_minimal_skill_parses():
+    parsed = parse_skill_md(skill("name: my-skill\ndescription: Does a thing."))
+    assert parsed.name == "my-skill"
+    assert parsed.description == "Does a thing."
+    assert parsed.body.startswith("# Body")
+    assert parsed.metadata == {}
+    assert parsed.warnings == ()
+
+
+def test_all_known_fields_parse():
+    parsed = parse_skill_md(
+        skill(
+            "name: full\n"
+            "description: Full skill\n"
+            "license: MIT\n"
+            "compatibility: any agent\n"
+            "allowed-tools: Read Write\n"
+            "metadata:\n"
+            "  author: someone\n"
+            "  version: '1.0'"
+        )
+    )
+    assert parsed.license == "MIT"
+    assert parsed.compatibility == "any agent"
+    assert parsed.allowed_tools == "Read Write"
+    assert parsed.metadata == {"author": "someone", "version": "1.0"}
+
+
+def test_block_scalars():
+    folded = parse_skill_md(skill("name: a\ndescription: >\n  first line\n  second line"))
+    assert folded.description == "first line second line"
+    literal = parse_skill_md(skill("name: a\ndescription: |\n  first\n  second"))
+    assert literal.description == "first\nsecond"
+
+
+def test_quoted_values_and_inline_comments():
+    parsed = parse_skill_md(skill('name: a\ndescription: "Quoted: value" '))
+    assert parsed.description == "Quoted: value"
+    parsed = parse_skill_md(skill("name: a\ndescription: plain # a comment"))
+    assert parsed.description == "plain"
+
+
+def test_unknown_key_is_ignored_with_a_warning():
+    parsed = parse_skill_md(skill("name: a\ndescription: d\nfuture-key: x"))
+    assert parsed.warnings == ("Ignored unknown frontmatter key 'future-key'.",)
+
+
+def test_bom_and_crlf_are_accepted():
+    text = "---\r\nname: a\r\ndescription: d\r\n---\r\nBody"
+    assert parse_skill_md(text).body == "Body"
+
+
+@pytest.mark.parametrize(
+    "text,fragment",
+    [
+        ("name: a\ndescription: d", "no YAML frontmatter"),
+        ("---\nname: a\ndescription: d\n", "not closed"),
+        (skill("description: d"), "'name' is required"),
+        (skill("name: a"), "'description' is required"),
+        (skill("name: A_B\ndescription: d"), "lowercase letters"),
+        (skill("name: -a\ndescription: d"), "lowercase letters"),
+        (skill("name: a--b\ndescription: d"), "lowercase letters"),
+        (skill("name: a\ndescription: d\nname: b"), "duplicate frontmatter key"),
+        (skill("name: a\ndescription: [x]"), "flow collections"),
+        (skill("name: a\ndescription: d\nmetadata: x"), "indented map"),
+        (skill("name: a\ndescription: d\nmetadata:\n  a: 1\n    b: 2"), "flat map"),
+        (skill("name: a\ndescription: d\nmetadata:\n  a: 1\n  a: 2"), "duplicate metadata key"),
+        (skill("name: a\ndescription: \"unterminated"), "unterminated"),
+        (skill("name: a\ndescription: d\n\tbad: x"), "tab"),
+        (skill("name: a\ndescription: d") + "\x00", "NUL"),
+    ],
+)
+def test_malformed_skills_are_rejected_with_a_reason(text, fragment):
+    with pytest.raises(SkillFormatError) as error:
+        parse_skill_md(text)
+    assert fragment in str(error.value)
+
+
+def test_overlong_fields_are_rejected():
+    with pytest.raises(SkillFormatError):
+        parse_skill_md(skill(f"name: {'a' * (limits.NAME_MAX_CHARS + 1)}\ndescription: d"))
+    with pytest.raises(SkillFormatError):
+        parse_skill_md(skill(f"name: a\ndescription: {'d' * (limits.DESCRIPTION_MAX_CHARS + 1)}"))
+
+
+def test_metadata_entry_cap():
+    entries = "\n".join(f"  k{i}: v" for i in range(limits.METADATA_MAX_ENTRIES + 1))
+    with pytest.raises(SkillFormatError):
+        parse_skill_md(skill(f"name: a\ndescription: d\nmetadata:\n{entries}"))
+
+
+def test_frontmatter_scan_is_bounded():
+    padding = "\n".join("# c" for _ in range(limits.FRONTMATTER_MAX_LINES + 5))
+    with pytest.raises(SkillFormatError):
+        parse_skill_md(f"---\nname: a\ndescription: d\n{padding}\n---\nBody")