feat: add --manifest-source flag to run and deploy commands

[srtaalej]

Summary

• Adds --manifest-source flag to slack run and slack deploy with values project or remote
• Resolves manifest differences non-interactively using the specified source
• Validates the flag value in PreRunE and provides clear error messaging
• Updates non-TTY error remediation to reference --manifest-source instead of --force/--force-remote

Test plan

• Verify --manifest-source=project resolves manifest diffs using local project
• Verify --manifest-source=remote resolves manifest diffs using remote app settings
• Verify invalid values produce clear error with remediation
• Verify existing --force and --force-remote flags still work
• Unit tests pass (make test)

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.39%. Comparing base (b5982b9) to head (3eb0447).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/app/status.go	85.48%	5 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #649      +/-   ##
==========================================
+ Coverage   72.26%   72.39%   +0.12%     
==========================================
  Files         238      239       +1     
  Lines       20072    20135      +63     
==========================================
+ Hits        14505    14576      +71     
+ Misses       4298     4283      -15     
- Partials     1269     1276       +7     

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