fix: progress always at 0% and context cancelled before sendDocument

- Fix progress template: remove spurious stderr: prefix and switch to
  _percent_str/_speed_str/_eta_str keys (progress.percent outputs NA
  for HLS streams with unknown total size)
- Update progress regex to match new template format:
  DLPROG| 45.2%|   1.05MiB/s|00:45
- Fix context cancellation bug: clearActiveJob was cancelling dlCtx
  before handleDownloadCompletion could send the document
- Update progress test cases to match new template output format

internal/dl/progress.go

@@ -12,7 +12,7 @@ import (
 )
 
 var progressRE = regexp.MustCompile(`\[\w+\]\s+([\d.]+)%\s+of\s+~?([\d.]+)(\w+)`)
-var progressTemplateRE = regexp.MustCompile(`^DLPROG\|([\d.]+)\|(.*?)\|(.*)$`)
+var progressTemplateRE = regexp.MustCompile(`^DLPROG\|\s*([\d.]+)%\|\s*(.*?)\s*\|(.*)$`)
 
 type progressUpdate struct {
 	pct   float64