[DISCORDSH] End-to-end testing with live GitHub repo data

[h0lybyte]

Parent

Part of #7849

Description

Test the full pipeline (Vault → GitHub API → Discord Embeds) against a live GitHub repository to validate data accuracy, embed formatting, and error handling.

Acceptance Criteria

• Notice Board embed renders correctly with real issue data
• Task Board embed renders correctly with real PR/milestone data
• Stagnation detection fires accurately
• Vault secret retrieval works in deployed environment
• Error states (bad PAT, API rate limit, missing repo) handled gracefully

[h0lybyte]

Unit test coverage landed via PR #8174 (46 tests). Expanded tracking in #8150.

Remaining:

• Error mapping tests (HTTP status → JediError)
• Rate limit header parsing tests
• Integration tests with live GitHub API
• Bot command tests (requires running bot)

[h0lybyte]

Mockoon-based docker-compose POC for local E2E testing tracked in #8180.

[h0lybyte]

Unit and mock HTTP tests cover the code paths (57 tests across PRs #8174 and #8179). Remaining integration and bot command tests deferred to docker-compose Mockoon POC in #8180.