Add NO_PROGRESS environment variable to disable progress bars

Add support for NO_PROGRESS environment variable to disable progress
bars, similar to how COLOR controls ANSI styling. This is particularly
useful for testing and CI environments.

Changes:
- maven/resolver.py: Check NO_PROGRESS env var before showing progress
- bin/test.sh: Set NO_PROGRESS=1 by default for CLI tests

Progress bars are now disabled when:
- --quiet flag is used
- NO_PROGRESS environment variable is set (any value)
- Content-Length header is missing or zero

All 518 tests passing.

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

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

Author: ctrueden

bin/test.sh

@@ -48,10 +48,11 @@ if [ ${#prysk_args[@]} -gt 0 ] && command -v prysk; then
   # Use `uv tool install prysk` instead.
   #
   # We set COLOR=never by default to avoid ANSI codes in test output.
+  # We set NO_PROGRESS=1 to disable progress bars in test output.
   # This is especially important for CI, which may or may not detect
   # as ANSI-color-compatible compared to local usage of prysk.
   # Tests can override this (e.g., color.t does).
-  COLOR="${COLOR:-never}" prysk -v "${prysk_args[@]}"
+  COLOR="${COLOR:-never}" NO_PROGRESS="${NO_PROGRESS:-1}" prysk -v "${prysk_args[@]}"
   prysk_status=$?
   if [ $prysk_status -ne 0 ]; then
     exit_status=$prysk_status

src/jgo/maven/resolver.py

@@ -316,8 +316,14 @@ def download(self, artifact: Artifact) -> Path | None:
                 # Get total size from Content-Length header
                 total_size = int(response.headers.get("content-length", 0))
 
-                # Show progress bar unless in quiet mode
-                show_progress = not is_quiet() and total_size > 0
+                # Show progress bar unless in quiet mode or NO_PROGRESS is set
+                import os
+
+                show_progress = (
+                    not is_quiet()
+                    and total_size > 0
+                    and not os.environ.get("NO_PROGRESS")
+                )
 
                 if show_progress:
                     # Create progress bar for this download