Interior comments, fragment comments, get_siblings + doc_gen comment support

Parser: read_value/read_list now capture Comment nodes inside lists
when ~comments:true. Module-level _preserve_comments ref threads the
flag through the recursive descent without changing signatures.

Pretty printer: has_interior_comments (recursive) forces multi-line
when any nested list contains comments. Comment nodes inside lists
emit as indented comment lines.

Edit tools: separate_comments strips interior comments recursively
via strip_interior_comments before passing to tree-tools (paths stay
correct). extract_fragment_comments parses new source with comments,
attaches leading comments to the target position in the comment map.

sx_get_siblings: injects comments for top-level siblings.

sx_doc_gen: parses with comments, tracks preceding Comment node,
includes cleaned comment text in generated component documentation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/lib/sx_parser.ml

@@ -110,7 +110,35 @@ let try_number str =
   | Some n -> Some (Number n)
   | None -> None
 
+(* Module-level flag — when true, comments are captured as Comment nodes.
+   Set by parse_all ~comments:true, reset after. *)
+let _preserve_comments = ref false
+
+(* Collect consecutive comment lines into a Comment node *)
+let collect_comment_node s =
+  let lines = ref [] in
+  let rec go () =
+    skip_whitespace s;
+    if not (at_end s) && s.src.[s.pos] = ';' then begin
+      lines := read_comment s :: !lines;
+      go ()
+    end
+  in
+  go ();
+  Comment (String.concat "\n" (List.rev !lines))
+
 let rec read_value s : value =
+  (* In comment-preserving mode, check for comments first *)
+  if !_preserve_comments then begin
+    skip_whitespace s;
+    if not (at_end s) && s.src.[s.pos] = ';' then
+      collect_comment_node s
+    else
+      read_value_core s
+  end else
+    read_value_core s
+
+and read_value_core s : value =
   skip_whitespace_and_comments s;
   if at_end s then begin
     let line = ref 1 in
@@ -184,14 +212,29 @@ and read_list s close_char =
   advance s; (* skip opening paren/bracket *)
   let items = ref [] in
   let rec go () =
-    skip_whitespace_and_comments s;
-    if at_end s then raise (Parse_error "Unterminated list");
-    if s.src.[s.pos] = close_char then begin
-      advance s;
-      List (List.rev !items)
+    if !_preserve_comments then begin
+      skip_whitespace s;
+      if at_end s then raise (Parse_error "Unterminated list");
+      if s.src.[s.pos] = close_char then begin
+        advance s;
+        List (List.rev !items)
+      end else if s.src.[s.pos] = ';' then begin
+        items := collect_comment_node s :: !items;
+        go ()
+      end else begin
+        items := read_value_core s :: !items;
+        go ()
+      end
     end else begin
-      items := read_value s :: !items;
-      go ()
+      skip_whitespace_and_comments s;
+      if at_end s then raise (Parse_error "Unterminated list");
+      if s.src.[s.pos] = close_char then begin
+        advance s;
+        List (List.rev !items)
+      end else begin
+        items := read_value s :: !items;
+        go ()
+      end
     end
   in go ()
 
@@ -220,42 +263,25 @@ and read_dict s =
 
 
 (** Parse a string into a list of SX values.
-    When [~comments:true], top-level ;; comments are preserved as [Comment]
-    nodes in the result list.  Default is [false] (strip comments). *)
+    When [~comments:true], comments are preserved as [Comment] nodes —
+    both at top level and inside lists.  Default is [false] (strip). *)
 let parse_all ?(comments=false) src =
+  _preserve_comments := comments;
   let s = make_state src in
   let results = ref [] in
   let rec go () =
-    if comments then begin
-      skip_whitespace s;
-      if at_end s then List.rev !results
-      else if s.src.[s.pos] = ';' then begin
-        (* Collect consecutive comment lines into one Comment node *)
-        let lines = ref [] in
-        let rec collect () =
-          skip_whitespace s;
-          if not (at_end s) && s.src.[s.pos] = ';' then begin
-            lines := read_comment s :: !lines;
-            collect ()
-          end
-        in
-        collect ();
-        let text = String.concat "\n" (List.rev !lines) in
-        results := Comment text :: !results;
-        go ()
-      end else begin
-        results := read_value s :: !results;
-        go ()
-      end
-    end else begin
-      skip_whitespace_and_comments s;
-      if at_end s then List.rev !results
-      else begin
-        results := read_value s :: !results;
-        go ()
-      end
+    if !_preserve_comments then skip_whitespace s
+    else skip_whitespace_and_comments s;
+    if at_end s then (
+      _preserve_comments := false;
+      List.rev !results
+    ) else begin
+      results := read_value s :: !results;
+      go ()
     end
-  in go ()
+  in
+  try go ()
+  with e -> _preserve_comments := false; raise e
 
 (** Parse a file into a list of SX values. *)
 let parse_file ?(comments=false) path =