fix: Stop deleting estimation files on transient errors (#1721)

* fix: Stop deleting estimation files on transient errors

Fixes #1543

Changes:
- Remove destructive File.Delete call that was triggered by any exception
- Validate file name format before parsing (check for '-Sub-' presence)
- Only catch IOException for transient errors (file locked, etc.)
- Skip gracefully on any error instead of deleting potentially valid files

The previous behavior would delete timing estimation files for transient errors
like file locks, causing permanent loss of timing data. Files should only be
overwritten by SaveSubModuleTimeAsync with correct data, not deleted on read errors.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: Expand exception handling to include permission errors

Address review feedback - catch additional file access exceptions:
- IOException (file locked, path too long, etc.)
- UnauthorizedAccessException (access denied)
- SecurityException (missing permissions)

Uses exception filter pattern for clean multi-exception handling.

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines/Engine/FileSystemModuleEstimatedTimeProvider.cs

@@ -40,13 +40,22 @@ public async Task<IEnumerable<SubModuleEstimation>> GetSubModuleEstimatedTimesAs
             {
                 try
                 {
-                    var name = Path.GetFileNameWithoutExtension(file.FullName).Split("-Sub-")[1];
+                    var fileNameWithoutExtension = Path.GetFileNameWithoutExtension(file.FullName);
+                    var subIndex = fileNameWithoutExtension.IndexOf("-Sub-", StringComparison.Ordinal);
+
+                    if (subIndex < 0)
+                    {
+                        // File doesn't match expected naming pattern - skip gracefully
+                        return null;
+                    }
+
+                    var name = fileNameWithoutExtension[(subIndex + 5)..]; // 5 = length of "-Sub-"
                     var time = await GetEstimatedTimeAsync(file.FullName).ConfigureAwait(false);
                     return new SubModuleEstimation(name, time);
                 }
-                catch
+                catch (Exception ex) when (ex is IOException or UnauthorizedAccessException or System.Security.SecurityException)
                 {
-                    File.Delete(file.FullName);
+                    // File access error (locked, permissions, etc.) - skip gracefully without deleting
                     return null;
                 }
             })