Fix GitHub Remote MCP auth test returning empty gh api output

[Copilot]

Remote MCP server initialization fails with "invalid session" (400), but agent silently falls back to gh api which returns empty output with exit 0, causing false positive test passes.

Changes

Workflow Instructions (.github/workflows/github-remote-mcp-auth-test.md)

• Add explicit MCP tool availability check before running test
• Forbid fallback to gh api command - test must use MCP tools
• Add root cause analysis section to error reports (MCP server connection failure vs token auth vs missing tools)
• Include direct workflow run URL in error reports

Context

MCP Gateway continues startup even when GitHub backend fails to initialize:

[ERROR] [backend] Failed to create HTTP connection: github, error=...invalid session
[INFO] [startup] Starting in ROUTED mode
[INFO] [startup] Routes: /mcp/<server> for servers: [github safeoutputs]

Agent sees no GitHub tools available, falls back to gh api /repos/.../issues, gets empty output. Workflow succeeds but creates discussion about auth failure.

This fix prevents the fallback behavior. Follow-up work needed: MCP Gateway should fail startup when critical backends fail.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[deep-report] Fix GitHub Remote MCP auth test returning empty gh api output</issue_title>
<issue_description>Description: The GitHub Remote MCP Authentication Test failed with gh api returning empty output despite exit code 0. Review the workflow token permissions and MCP server availability, and add explicit auth validation or a local-mode fallback to avoid silent failures.

Expected Impact: Restores daily MCP auth coverage and prevents false positives in auth monitoring.

Suggested Agent: MCP integration agent

Estimated Effort: Quick (< 1 hour)

Data Source: DeepReport Intelligence Briefing 2026-01-20; discussion #10821 (run §21170454994).

AI generated by DeepReport - Intelligence Gathering Agent

Comments on the Issue (you are @copilot in this section)

• Fixes [deep-report] Fix GitHub Remote MCP auth test returning empty gh api output #10864

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