Add diagnostic logging to synctex to identify failure cause

Logs: request params, directory used, whether output.synctex.gz
is found, and the actual synctex binary output or error.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/clsi/app/js/CompileManager.js

@@ -563,6 +563,10 @@ async function _runSynctex(projectId, userId, command, opts) {
   const compileGroup = runInOutputDir ? 'synctex-output' : 'synctex'
   const defaultImageName =
     Settings.clsi && Settings.clsi.docker && Settings.clsi.docker.image
+  logger.warn(
+    { projectId, userId, buildId, editorId, directory, command, runInOutputDir },
+    'synctex: starting request'
+  )
   // eslint-disable-next-line @typescript-eslint/return-await
   return await OutputCacheManager.promises.queueDirOperation(
     outputDir,
@@ -573,6 +577,7 @@ async function _runSynctex(projectId, userId, command, opts) {
       let downloadedFromCache = false
       try {
         await _checkFileExists(directory, 'output.synctex.gz')
+        logger.warn({ directory }, 'synctex: output.synctex.gz found')
         if (compileFromClsiCache) {
           try {
             await _checkFileExists(directory, 'output.log')
@@ -581,6 +586,10 @@ async function _runSynctex(projectId, userId, command, opts) {
           }
         }
       } catch (err) {
+        logger.warn(
+          { err: err.message, directory },
+          'synctex: output.synctex.gz not found'
+        )
         if (
           err instanceof Errors.NotFoundError &&
           compileFromClsiCache &&
@@ -618,11 +627,13 @@ async function _runSynctex(projectId, userId, command, opts) {
           compileGroup,
           null
         )
+        logger.warn({ command, stdout }, 'synctex: command output')
         return {
           stdout,
           downloadedFromCache,
         }
       } catch (error) {
+        logger.warn({ err: error.message, command }, 'synctex: command failed')
         throw OError.tag(error, 'error running synctex', {
           command,
           projectId,