feat: complete BLOCK_LIST/ADDR_LIST keywords and space comments

Add keyword-driven completions for BLOCK_LIST and ADDR_LIST in the LSP server.
- While typing a prefix of these keywords the server returns the keyword(s)
  as incomplete snippet suggestions that trigger a re-request.
- Once the keyword is typed the server replaces it with a full list of the
  corresponding loaded block templates or addresses (quoted), and sets each
  item's filter_text to include the keyword so further typing narrows results.
- Integrate this flow into on_completion and factor the symbol-list logic
  into a helper that returns either incomplete keyword suggestions or the
  completed symbol list.

Also implement NxFormatter.format_comment to ensure a single space after a
leading '#' for comments that don't already start with whitespace, while
leaving sequences of '#' (separators), shebangs, and already-spaced comments
unchanged. This affects both standalone and inline comments.

Add/rename tests to cover the new completions and comment-spacing behavior.

server/src/tools/formatter.py

@@ -12,6 +12,14 @@ class NxFormatter(BaseFormatter):
     while leaving all other formatting behavior unchanged.
     """
 
+    def format_comment(self, comment) -> List[str]:  # type: ignore[override]
+        # "#Comment" -> "# Comment". Leave "#", "##..." separators, "#!" and
+        # comments that already start with whitespace untouched.
+        value = comment.value
+        if value and not value[0].isspace() and value[0] not in "#!":
+            value = " " + value
+        return [f"#{value}"]
+
     def format_braced_expression(self, expr) -> List[str]:  # type: ignore[override]
         # This method mirrors BaseFormatter.format_braced_expression but inserts
         # a line continuation (" \") between continuation lines similar to