docs: update SUPPORT.md, fix issue templates, add preset submission template (#1910)

* docs: update SUPPORT.md, fix issue templates, add preset submission template

- SUPPORT.md: simplify structure, add Discussions link, soften response commitment
- config.yml: fix broken Extension Development Guide URL (was manfredseee → github)
- agent_request.yml: update agent list with Tabnine, Vibe, Kimi, Trae, Pi, iFlow
- preset_submission.yml: new issue template for preset catalog submissions

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>