fix slack notification workflow

[lkostrowski]

mention on slack only if workflow fails

[changeset-bot]

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Latest commit: e72a306

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[Copilot]

Pull request overview

Updates Slack notification behavior in deployment workflows so the Slack mention is only applied when the workflow fails, matching the stated intent for reduced noise during successful runs.

Changes:

• Add mention_on: failure to the notify-slack reusable workflow invocation for staging/release deployments
• Add mention_on: failure to the notify-slack invocation for master-staging deployments
• Add mention_on: failure to the notify-slack invocation for cloud deployments

Reviewed changes

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

File	Description
.github/workflows/deploy-staging-and-prepare-release.yaml	Configure Slack notification mentions to trigger only on failure for staging + prepare-release flow.
.github/workflows/deploy-master-staging.yaml	Configure Slack notification mentions to trigger only on failure for master-staging deployments.
.github/workflows/deploy-cloud.yaml	Configure Slack notification mentions to trigger only on failure for cloud deployments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.67%. Comparing base (8c5f075) to head (e72a306).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6359   +/-   ##
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  Coverage   42.67%   42.67%           
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  Files        2517     2517           
  Lines       43696    43696           
  Branches    10341    10380   +39     
=======================================
  Hits        18647    18647           
  Misses      23719    23719           
  Partials     1330     1330           

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