fix(pdftract-1j0f8): prevent newline accumulation in CLI reference generator

The gen-cli-reference binary was accumulating extra blank lines after
the <!-- AUTOGEN END --> marker on each regeneration because it
preserved all content after the marker (including leading whitespace)
and then added its own newlines.

Fix: Trim leading whitespace from hand-curated content before appending.

Also regenerated cli-reference.md to remove accumulated blank lines.

Closes pdftract-1j0f8

crates/pdftract-cli/src/bin/generate-cli-reference.rs

@@ -54,7 +54,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let hand_curated_content = if output_path.exists() {
         let existing = fs::read_to_string(&output_path)?;
         if let Some(idx) = existing.find(AUTOGEN_END_MARKER) {
-            Some(existing[idx + AUTOGEN_END_MARKER.len()..].to_string())
+            // Trim leading whitespace from curated content to prevent newline accumulation
+            Some(existing[idx + AUTOGEN_END_MARKER.len()..].trim_start().to_string())
         } else {
             None
         }

docs/user-docs/src/cli-reference.md

@@ -612,8 +612,6 @@ Exit code policy: exits 0 if no checks FAIL (WARN does not affect exit code); ex
 
 <!-- AUTOGEN END -->
 
-
-
 ## Hand-Curated Content
 
 > **Note:** Any content added after this marker will be preserved