fix: address PR #332 review feedback

Addresses 12 of 13 review comments from Copilot and CodeRabbit on
PR #332. One comment (no-manifests in validate-plugins.yml) is
declined and answered inline; the rest are applied here.

Substantive fixes:

- .github/workflows/validate-plugins.yml — add --noconftest to the
  schema-tests step. tests/conftest.py imports structlog at module
  level, but the CI job only installs requirements-test.txt
  (pytest/httpx/jsonschema), so pytest collection would fail at
  conftest import. The schema tests don't use shared fixtures, so
  skipping conftest is safe and avoids dragging the full runtime
  requirements into a 2 KB validation job. (Copilot)

- schema/plugin.schema.json — tighten the server_files regex on both
  settings.server_files and diagnostics.server_files to match the
  runtime _validate_relpath rules in plugins/__init__.py. The
  previous regex only blocked absolute paths, drive letters,
  backslashes, and "..". The runtime also rejects "//", "./",
  "/./", and leading-dotfile segments. Schema-valid manifests are
  now also load-time-valid. Verified the regex against 12 cases:
  the 3 in-tree manifests still validate. (Copilot)

- .claude/skills/plugin-validate/SKILL.md — add a per-iteration
  plugin_ok flag so we no longer print "OK <path>" after an earlier
  FAIL in the same manifest. Schema-pass + id-mismatch previously
  produced both FAIL and OK lines for one plugin. (CodeRabbit)

- docs/websocket-protocol.md — clarify song_info.tuning array length
  is source-dependent (typically 6 guitar, 4 bass, but extended-range
  GP imports can be 7/8/5/6). Recommend highway.getStringCount() for
  the authoritative count. Line 30 already said this; the table row
  on line 12 was the stale half. (CodeRabbit)

Trivial fixes:

- .claude/rules/plugin-author.md — "wants included" -> "wants to
  include" in the settings.server_files rule. (CodeRabbit)

- Markdown MD040 — add `text` language tags to 7 bare-fence code
  blocks across AGENTS.md, docs/PLUGIN_AUTHORING.md,
  docs/testing-plugins.md, docs/plugin-logging.md, .claude/README.md,
  .claude/agents/slopsmith-reviewer.md, and
  .claude/skills/plugin-validate/SKILL.md (two fences). (CodeRabbit)

Declined:

- .github/workflows/validate-plugins.yml no-manifests -> exit 0
  (CodeRabbit suggested exit 1). Plugins in this repo are in-tree,
  not submodules (no .gitmodules, git submodule status empty), and
  the workflow has a path filter on plugins/**/plugin.json so it
  only runs when a manifest actually changes. Exit 0 is correct.
  Answered inline on the PR.

Verification:
  pytest tests/test_plugin_schema.py -v --noconftest    # 8 passed
  python -c "import json,glob,jsonschema; s=json.load(open('schema/plugin.schema.json')); [jsonschema.validate(json.load(open(p)), s) for p in sorted(glob.glob('plugins/*/plugin.json'))]"
  # ok — all 3 in-tree manifests validate against tightened schema
Signed-off-by: Miguel_LZPF <mgcdreamer@gmail.com>

.claude/skills/plugin-validate/SKILL.md

@@ -31,6 +31,7 @@ for path in sorted(glob.glob('plugins/*/plugin.json')):
     plugin_dir = pathlib.Path(path).parent
     plugin_id = plugin_dir.name
     m = json.load(open(path))
+    plugin_ok = True  # per-iteration flag so we don't print OK after a later FAIL
     # 1. Schema
     try:
         jsonschema.validate(m, schema)
@@ -42,16 +43,19 @@ for path in sorted(glob.glob('plugins/*/plugin.json')):
     if m['id'] != plugin_id:
         print(f"FAIL {path}: id={m['id']!r} but directory is {plugin_id!r}")
         ok = False
+        plugin_ok = False
     # 3. Declared files exist
     for field in ('script', 'routes', 'tour'):
         if field in m and not (plugin_dir / m[field]).exists():
             print(f"FAIL {path}: {field}={m[field]!r} but file missing")
             ok = False
+            plugin_ok = False
     if 'settings' in m and 'html' in m['settings']:
         h = m['settings']['html']
         if not (plugin_dir / h).exists():
             print(f"FAIL {path}: settings.html={h!r} but file missing")
             ok = False
+            plugin_ok = False
     for field in ('settings', 'diagnostics'):
         if field in m and 'server_files' in m[field]:
             for relpath in m[field]['server_files']:
@@ -61,7 +65,9 @@ for path in sorted(glob.glob('plugins/*/plugin.json')):
                 if '..' in relpath or relpath.startswith('/') or '\\' in relpath:
                     print(f"FAIL {path}: {field}.server_files contains unsafe path {relpath!r}")
                     ok = False
-    print(f"OK   {path}")
+                    plugin_ok = False
+    if plugin_ok:
+        print(f"OK   {path}")
 sys.exit(0 if ok else 1)
 PY
 ```
@@ -84,13 +90,13 @@ pytest tests/test_plugin_schema.py::test_schema_license_enum_subset_of_contribut
 
 Use the format from the script: `OK <path>` per validated manifest, `FAIL <path>: <reason>` per failure. Add a one-line summary:
 
-```
+```text
 Result: 3/3 plugins valid (OK app_tour_library, app_tour_settings, highway_3d)
 ```
 
 or
 
-```
+```text
 Result: 2/3 plugins valid; 1 FAIL (see above)
 ```