[INFRA] Improve Discord merge summary text

[egdev6]

Area

GitHub Actions / CI

Team

Squad 1

Milestone

MVP

Motivation

The Discord merge notification is delivered, but the embed can be too vague because it may use the first non-empty PR body line instead of the actual PR summary. The Discord message should clearly explain what changed.

Proposed change

Files/config affected:

• .github/workflows/discord-merge-notify.yml

Expected behavior:

• Discord notifications include a clear Spanish Qué cambió section.
• The workflow extracts useful bullets from the PR body ## Summary section when available.
• If no PR summary exists, the workflow falls back to commit messages or commit text.
• The message includes changed-file count and a short changed-files preview.

Secrets or environment assumptions:

• Uses existing DISCORD_WEBHOOK_URL repository secret.

Rollback plan:

• Revert the workflow change.

Validation plan

Local commands:

• Parse workflow YAML.
• Extract the github-script body and run node --check.
• git diff --check.

Workflow run URL or draft PR check:

• Confirm PR checks pass.
• After merge, Discord run should produce a clearer embed.

Failure/rollback check:

• Workflow should still skip safely when DISCORD_WEBHOOK_URL is absent.

Workflow gates

• START WORK must run only after issue label status:approved; it assigns the issue, moves Project status to In progress, and records branch/worktree before implementation.
• PR must link this issue and include validation evidence.
• END WORK moves the Project item to Done only after merge or explicit maintainer approval.

Additional notes

This improves the already-merged Discord notification workflow; it does not change the webhook secret handling.

Related resources

• Previous workflow PR: feat(discord): add merge notification workflow #246