community: CODEOWNERS, issue and PR templates, code of conduct, claiming issues; CI on pull requests from forks

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

.github/ISSUE_TEMPLATE/bug.yml

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+name: Bug report
+description: Something FieldCraft does wrong, or a crash
+labels: [bug]
+body:
+  - type: textarea
+    id: what
+    attributes:
+      label: What happened
+      description: What you did, what you expected, and what FieldCraft did instead.
+    validations:
+      required: true
+  - type: textarea
+    id: reproduce
+    attributes:
+      label: How to reproduce
+      description: The commands, script, `.fieldcraft` or `.solidcraft` file that shows it. For a crash, attach the crash report folder (`fieldcraft-cli crashes`).
+  - type: input
+    id: version
+    attributes:
+      label: Version and platform
+      placeholder: "v0.1.0, macOS 15 arm64"

.github/ISSUE_TEMPLATE/config.yml

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+blank_issues_enabled: false

.github/ISSUE_TEMPLATE/feature.yml

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+name: Feature request
+description: A capability FieldCraft should have
+labels: [enhancement]
+body:
+  - type: textarea
+    id: need
+    attributes:
+      label: What you need and why
+      description: The analysis or workflow you are trying to do.
+    validations:
+      required: true
+  - type: textarea
+    id: reference
+    attributes:
+      label: References
+      description: Papers, textbooks or published benchmarks that define the behaviour. Do not paste text, files or results from commercial CAE products.