feat(mailgun): add US/EU region selection to the Mailgun block and tools

[waleedlatif1]

Summary

• Added a Region dropdown (US / EU, default US) to the Mailgun block, shown for every operation
• Added an optional region param (user-only) to all 8 Mailgun tools; each request.url now resolves its host through one shared getMailgunApiBaseUrl helper in tools/mailgun/utils.ts
• EU maps to https://api.eu.mailgun.net/v3; anything else (including no value) stays on https://api.mailgun.net/v3, so existing workflows keep calling the US host unchanged
• Regenerated tool metadata and the Mailgun integration docs

Closes #8420

Type of Change

• New feature

Testing

• Routed every operation (all 8) through the real block tools.config.tool/params → tool request.url for three states: legacy block with no region value, us, and eu. All 24 resolved to the expected host, including add_list_member (the one operation that remaps params)
• Hit both live hosts with an invalid key: api.mailgun.net and api.eu.mailgun.net both answer 401, so both are real endpoints
• Deploy change detection resolves a field added after deploy against the current definition's default on both sides, so already-deployed Mailgun workflows do not flip to "needs redeploy"
• bun run type-check (apps/sim), bun run lint, block-registry check, bun run check:audits (52/52), docs-manifest:check
• vitest run blocks/ tools/index.test.ts tools/utils.test.ts tools/params.test.ts lib/workflows/comparison: 1017 passed

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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Project	Deployment	Actions	Updated
docs	Ready	Preview	Sep 29, 2026 7:26pm UTC

[cubic-dev-ai]

No issues found across 13 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Re-trigger cubic}

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adds region selection to Mailgun integration tools.

The PR appears safe to merge; no new actionable issue was identified.

Summary

The PR adds a US/EU region selector to the Mailgun block and routes all eight Mailgun tools through a shared host-selection helper.

• Omitted regions continue to use the US endpoint.
• Tool metadata and integration documentation include the new parameter.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[Mailgun block region or user-provided tool parameter] --> B[Mailgun tool request URL]
  B --> C{Region is eu?}
  C -- Yes --> D[EU API host]
  C -- No or omitted --> E[US API host]

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_{Reviews (2) · Last reviewed commit: "feat(mailgun): add US/EU region selectio..."}

[waleedlatif1]

@greptile