bug(contributing): support links point to disabled Discussions

[dnlrsls]

📝 Bug Description

Contributor instructions and the GitHub issue chooser send general questions/support to this repository's Discussions page, but GitHub currently reports has_discussions: false. That advertised exit is unavailable. This is distinct from tracked questions that require maintainer work and from the private vulnerability reporting route. The observation was rechecked against main at c61f601ee9cc3a9cba6abbedd6bef2382318eada.

🔄 Steps to Reproduce

1. Read CONTRIBUTING.md's issue-first guidance: it directs general questions and support to https://github.com/Gentleman-Programming/engram/discussions.
2. Read .github/ISSUE_TEMPLATE/config.yml: its Questions & Discussions contact link points to the same URL. The markdown in .github/ISSUE_TEMPLATE/tracked_question.yml repeats the instruction.
3. Query the repository setting with gh api repos/Gentleman-Programming/engram --jq .has_discussions and observe false.

✅ Expected Behavior

A contributor following an advertised support route reaches a working channel. Either enable the intended Discussions capability or update the guidance and issue chooser to a real supported path. Preserve the distinction between general support and questions that warrant tracked work; do not replace a broken exit with another unverified link.

❌ Actual Behavior

The three surfaces above send contributors to Discussions while that repository feature is disabled. has_discussions returns false; the issue chooser offers a contact route that cannot serve its advertised purpose.

Operating System

Windows

Engram Version

2.2.1 (installed CLI); repository guidance verified on main@c61f601

Agent / Client

Other

📋 Relevant Logs

$ gh api repos/Gentleman-Programming/engram --jq .has_discussions
false

💡 Additional Context

Issue #1359 only added a link from AGENTS.md to CONTRIBUTING.md; it did not make the linked support exit functional. This issue asks for one working contributor-support route and aligned references, not a new generalized workflow or automatic issue approval. Validate the chosen route from a contributor's perspective before closing.

[dnlrsls]

Resolved by enabling GitHub Discussions for this repository. The public Discussions page is reachable and the General and Q&A categories are configured, so the existing contributor guidance now points to an available support channel. We closed #1491 without merging because its proposed issue-chooser link would return visitors to the chooser itself. No documentation change is needed for this issue.