Require contributors to disclose authoring environment and target dev

Add a mandatory self-identification disclosure (model, harness, harness
version, all installed plugins) to the PR template and all three issue
templates, and document the requirement in the contributor guidelines.
We weigh contributions differently depending on what produced them:
content reasoned from documentation is held to a different bar than work
grounded in a real session.

Also state explicitly, in both CLAUDE.md and the PR template, that all
PRs must target the dev branch rather than main.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -12,14 +12,17 @@ add a comment or reaction to the existing one instead.
 
 - [ ] I searched existing issues and this is not a duplicate
 
-## Environment
+## Environment (required)
+<!-- Required. We assume an agent filed this report — tell us which one and
+     where it ran. We weigh reports by what produced them. -->
 
 | Field | Value |
 |-------|-------|
 | Superpowers version | |
 | Harness (Claude Code, Cursor, etc.) | |
 | Harness version | |
-| Model | |
+| Your model + version | |
+| All plugins installed | |
 | OS + shell | |
 
 ## Is this a Superpowers issue or a platform issue?