fix: move cargo-wdk output to stderr

[gurry]

Makes it consistent with cargo and rustc. Fixes #526

[Copilot]

Pull request overview

This PR moves cargo-wdk's human-readable output from stdout to stderr to align with standard conventions used by cargo, rustc, and other build tools. This change enables stdout to be reserved for machine-readable output in the future and prevents output from being split across streams when redirected.

• Configured the tracing subscriber to write to stderr instead of stdout
• Updated all test assertions to verify output on stderr instead of stdout

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/cargo-wdk/src/trace.rs	Added .with_writer(std::io::stderr) to the tracing subscriber configuration to redirect all cargo-wdk output to stderr
crates/cargo-wdk/tests/build_command_test.rs	Updated test assertions to check stderr instead of stdout for cargo-wdk build output messages
crates/cargo-wdk/tests/new_command_test.rs	Updated test assertions to check stderr instead of stdout for cargo-wdk new command output messages

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.67%. Comparing base (dd8fdff) to head (9ae5782).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #599   +/-   ##
=======================================
  Coverage   82.67%   82.67%           
=======================================
  Files          25       25           
  Lines        7135     7136    +1     
  Branches     7135     7136    +1     
=======================================
+ Hits         5899     5900    +1     
  Misses       1107     1107           
  Partials      129      129           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[krishnakumar4a4]

lgtm