refactor: remove GetBookMetadata tool; fix BookContentTool foreach->Select

- Remove GetBookMetadata() MCP tool and trim BookMetadata class to SiteUrl only
- Fix PR #876 feedback: refactor foreach+clone into codeLines.Select(line => line.CloneNode(deep:true))

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

Author: BenjaminMichaelis

EssentialCSharp.Web/Tools/BookContentTool.cs

@@ -401,10 +401,8 @@ private static void ExtractNodeContent(HtmlNode node, StringBuilder sb)
             var codeLines = node.SelectNodes(".//div[contains(@class,'code-line')]");
             if (codeLines is not null)
             {
-                foreach (var line in codeLines)
+                foreach (var lineClone in codeLines.Select(line => line.CloneNode(deep: true)))
                 {
-                    // Clone to avoid mutating the live HtmlDocument DOM
-                    var lineClone = line.CloneNode(deep: true);
                     var lineNumberSpan = lineClone.SelectSingleNode(".//span[contains(@class,'code-line-number')]");
                     lineNumberSpan?.Remove();
                     sb.AppendLine(HtmlEntity.DeEntitize(lineClone.InnerText));

EssentialCSharp.Web/Tools/BookSearchTool.cs

@@ -9,15 +9,8 @@
 
 namespace EssentialCSharp.Web.Tools;
 
-// Book metadata constants — update here when edition changes.
 file static class BookMetadata
 {
-    public const string Title = "Essential C#";
-    public const string Edition = "9th Edition";
-    public const string CSharpVersion = "C# 13.0";
-    public const string Authors = "Mark and Benjamin Michaelis";
-    public const string Publisher = "Addison-Wesley Professional";
-    public const string Isbn13 = "978-0-13-576056-5";
     public const string SiteUrl = "https://essentialcsharp.com";
 }
 
@@ -175,23 +168,6 @@ public string GetDirectContentUrl(
                $"URL: {url}";
     }
 
-    [McpServerTool(Title = "Get Book Metadata", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
-     Description("Get citation-quality metadata for the Essential C# book: title, authors, edition, C# version covered, ISBN, publisher, and website URL. Use this when generating citations or when asked which edition or C# version the book covers.")]
-    public string GetBookMetadata()
-    {
-        return $"""
-                # {BookMetadata.Title} — Book Metadata
-
-                **Title:** {BookMetadata.Title}
-                **Edition:** {BookMetadata.Edition}
-                **C# Version:** {BookMetadata.CSharpVersion}
-                **Authors:** {BookMetadata.Authors}
-                **Publisher:** {BookMetadata.Publisher}
-                **ISBN-13:** {BookMetadata.Isbn13}
-                **Website:** {BookMetadata.SiteUrl}
-                """;
-    }
-
     [McpServerTool(Title = "Lookup Concept", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Find all sections in the Essential C# book that cover a specific C# concept. Combines section heading search with semantic vector search (when available) to give broad coverage. Returns section slugs, chapter numbers, and direct links.")]
     public async Task<string> LookupConcept(

EssentialCSharp.Web/Views/McpSetup/Index.cshtml

@@ -591,25 +591,6 @@
             </div>
         </details>
 
-        <details class="card mb-2">
-            <summary class="card-header d-flex align-items-center gap-2" style="cursor:pointer;list-style:none">
-                <span class="details-chevron">&#9656;</span>
-                <span class="font-monospace fw-semibold">get_book_metadata</span>
-                <span class="text-muted small ms-auto">Citation-quality book info</span>
-            </summary>
-            <div class="card-body">
-                <p class="card-text">
-                    Returns title, authors, edition, C# version covered, ISBN, publisher, and website URL.
-                    Useful when the AI needs to cite the book or answer "which edition is this?"
-                </p>
-                <dl class="row mb-0 small">
-                    <dt class="col-sm-3">Input</dt>
-                    <dd class="col-sm-9">None</dd>
-                    <dt class="col-sm-3">Returns</dt>
-                    <dd class="col-sm-9">Title, 9th Edition, C# 13, authors, ISBN-13, publisher, URL</dd>
-                </dl>
-            </div>
-        </details>
 
     </section>