feat(worker): session skill registry (install/update/remove, pinned clone)

src/ClaudeDo.Worker/Skills/SkillFrontmatter.cs

@@ -0,0 +1,62 @@
+namespace ClaudeDo.Worker.Skills;
+
+internal static class SkillFrontmatter
+{
+    public sealed record ParsedFrontmatter(string Name, string Description);
+
+    /// <summary>
+    /// Parses the YAML frontmatter block (between the first two "---" lines) of a SKILL.md
+    /// file, extracting "name" (required) and "description" (optional). The description may
+    /// be a folded scalar ("description: >"), whose indented continuation lines are joined
+    /// with spaces into a single string.
+    /// </summary>
+    public static ParsedFrontmatter Parse(string skillMdPath)
+    {
+        var lines = File.ReadAllLines(skillMdPath);
+        if (lines.Length == 0 || lines[0].Trim() != "---")
+            throw new InvalidOperationException($"'{skillMdPath}' has no YAML frontmatter block.");
+
+        string? name = null;
+        var description = "";
+
+        var i = 1;
+        for (; i < lines.Length; i++)
+        {
+            var line = lines[i];
+            if (line.Trim() == "---") break;
+
+            if (line.StartsWith("name:", StringComparison.Ordinal))
+            {
+                name = line["name:".Length..].Trim().Trim('"', '\'');
+            }
+            else if (line.StartsWith("description:", StringComparison.Ordinal))
+            {
+                var rest = line["description:".Length..].Trim();
+                if (rest == ">" || rest == ">-" || rest == "|" || rest == "|-")
+                {
+                    var folded = new List<string>();
+                    var j = i + 1;
+                    for (; j < lines.Length; j++)
+                    {
+                        var contLine = lines[j];
+                        if (contLine.Trim() == "---") break;
+                        if (contLine.Length == 0) continue;
+                        if (!char.IsWhiteSpace(contLine[0])) break;
+                        folded.Add(contLine.Trim());
+                    }
+                    description = string.Join(" ", folded);
+                    i = j - 1;
+                }
+                else
+                {
+                    description = rest.Trim('"', '\'');
+                }
+            }
+        }
+
+        if (string.IsNullOrWhiteSpace(name))
+            throw new InvalidOperationException($"'{skillMdPath}' frontmatter is missing required 'name'.");
+
+        return new ParsedFrontmatter(name, description);
+    }
+}