Show actual Python script output when smart match fails or succeeds

Instead of generic "possible causes", the terminal now shows the exact
output from the Python script:
- On empty results: full script log (shows which step failed and why)
- On success: script log shown below the match results
- On error: raw error output shown directly

The __log field is attached to the JSON result so the renderer always
has access to the script's diagnostic output.

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

Author: nodeeeeee

electron/main.js

@@ -1070,14 +1070,16 @@ function registerIpc() {
         const marker = '__MATCH_RESULT__';
         const idx = combined.indexOf(marker);
         if (idx < 0) {
-          console.error(`[align:suggestMatches] no marker:\n${combined.slice(-500)}`);
-          resolve({ __error: `No match results. Log: ${combined.slice(-300)}` });
+          resolve({ __error: combined.trim() || 'Script produced no output.' });
           return;
         }
         try {
-          resolve(JSON.parse(combined.slice(idx + marker.length).trim()));
+          const result = JSON.parse(combined.slice(idx + marker.length).trim());
+          // Attach the log so the UI can show it even on empty results
+          result.__log = combined.slice(0, idx).trim();
+          resolve(result);
         } catch (e) {
-          resolve({ __error: `JSON parse error: ${e.message}` });
+          resolve({ __error: `JSON parse error: ${e.message}\n\n${combined.trim()}` });
         }
       });
     });

electron/renderer/app.js

@@ -1510,26 +1510,26 @@ async function attachPageHandlers() {
         return;
       }
 
-      if (!matches || !Object.keys(matches).length) {
-        Term.write('\n✗ Smart match returned empty results.\n'
-          + 'Possible causes:\n'
-          + '  - pymupdf not installed (cannot read PDF slide text)\n'
-          + '  - sentence-transformers not installed (cannot embed text)\n'
-          + '  - No captions or materials found for this course\n'
-          + `  - Course dir: check if files exist under Output Dir / ${cid}\n`, 'warn');
-        snack('No embedding matches — see terminal for diagnostics.', false);
-        if (statusEl) statusEl.textContent = 'No matches — check terminal.';
+      // Filter out internal keys
+      const log = matches?.__log || '';
+      const matchKeys = Object.keys(matches).filter(k => !k.startsWith('__'));
+
+      if (!matchKeys.length) {
+        Term.write(`\n✗ Smart match returned no results.\n\n── Script output ──\n${log || '(empty)'}\n`, 'warn');
+        snack('No embedding matches — see terminal for details.', false);
+        if (statusEl) statusEl.textContent = 'No matches — see terminal.';
         return;
       }
 
       // Apply embedding suggestions to rows
       let updated = 0;
       for (const row of AlignState.rows) {
-        if (matches[row.stem]) {
+        if (matches[row.stem] && !row.stem.startsWith('__')) {
           row.slides = [matches[row.stem]];
           updated++;
         }
       }
+      if (log) Term.write(`\n── Smart match log ──\n${log}\n`, 'cmd');
       _alignRebuildRows();
       snack(`Smart match: ${updated}/${AlignState.rows.length} video(s) matched via ${model}.`);
     });