feat(cli): add stg alias for stage command

[mpyw]

Summary

• Add stg as an alias for the stage command

Usage

# These are now equivalent:
suve stage status
suve stg status

suve stage apply
suve stg apply

Test plan

• go test ./internal/cli/commands/stage/...

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.35%. Comparing base (387bc5c) to head (9755bc5).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #126   +/-   ##
=======================================
  Coverage   90.35%   90.35%           
=======================================
  Files         132      132           
  Lines        7745     7746    +1     
=======================================
+ Hits         6998     6999    +1     
  Misses        503      503           
  Partials      244      244           

Flag	Coverage Δ
e2e	67.77% <100.00%> (+<0.01%)	⬆️
platform-darwin	64.38% <ø> (ø)
platform-linux	62.85% <ø> (ø)
platform-windows	73.46% <ø> (ø)
unittests	79.69% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ 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.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.