M6: Merge data files into spreadsheet (FDF, XFDF, filled PDF forms → CSV); form_merge_data tool

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/commands.rs

@@ -201,6 +201,7 @@ pub const COMMANDS: &[CommandSpec] = &[
     c("comment.summarize", "Summarize comments", None, None, HasComments, "file-text"),
     c("form.import_data", "Import form data…", None, None, HasFields, "file-input"),
     c("form.export_data", "Export form data…", None, None, HasFields, "file-output"),
+    c("form.merge_data", "Merge data files into spreadsheet…", None, None, Nothing, "file-spreadsheet"),
     c("form.flatten", "Flatten form fields", None, None, HasFields, "layers"),
     c("form.prepare", "Prepare a form", None, None, Modification, "text-cursor-input"),
     c("form.tab_order.row", "Tab order: by rows", None, None, HasFields, "rows-3"),

crates/engine/src/lib.rs

@@ -82,6 +82,14 @@ pub use printcraft_sign as sign;
 pub use printcraft_sign::{SignOptions, SignatureInfo, Status as SignatureStatus, TrustStore};
 pub use printcraft_xfdf::Format as DataFormat;
 
+/// Forms ▸ Merge data files into spreadsheet: the field values of each file (FDF, XFDF or a
+/// filled-in PDF form), as CSV with one row per file.
+pub fn merge_data_files(files: &[(String, Vec<u8>)]) -> Result<String, String> {
+    let rows =
+        files.iter().map(|(name, bytes)| printcraft_xfdf::data_values(bytes).map_err(|e| format!("{name}: {e}"))).collect::<Result<Vec<_>, _>>()?;
+    Ok(printcraft_xfdf::merge_csv(&rows))
+}
+
 pub type SplitPart = (usize, usize, Arc<Vec<u8>>);
 
 use std::sync::Arc;