Add issue templates and disable blank issues

Four templates: bug report (with environment table and platform-vs-plugin
gate), feature request (with problem statement and core-appropriateness
question), IDE/platform support request, and a config that disables
blank issues and redirects questions to Discord.

.github/ISSUE_TEMPLATE/platform_support.md

@@ -0,0 +1,23 @@
+---
+name: IDE / Platform Support Request
+about: Request support for a new IDE, editor, or AI coding tool
+labels: platform-support
+---
+
+<!--
+BEFORE FILING: Search existing issues — your IDE may already be
+requested or discussed.
+-->
+
+- [ ] I searched existing issues for this IDE/platform
+
+## Which IDE or platform?
+<!-- Name and link -->
+
+## Does this tool have a plugin or extension system?
+<!-- If yes, link to the docs. If no, explain how third-party
+     integrations typically work with this tool. -->
+
+## Have you tried manual installation?
+<!-- Many tools work with Superpowers through manual setup even without
+     official support. Did you try? What happened? -->