chore: add community health files (Code of Conduct, issue templates)

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Report a bug or unexpected behavior
+title: ''
+labels: bug
+assignees: ''
+---
+
+## What happened
+<!-- A clear description of the bug. -->
+
+## Steps to reproduce
+<!-- Minimal steps, command, or code sample. -->
+
+## Expected behavior
+
+## Version & environment
+<!-- Release/commit, language runtime version, OS. -->
+
+## Additional context

.github/ISSUE_TEMPLATE/config.yml

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+blank_issues_enabled: true
+contact_links:
+  - name: Security vulnerability
+    url: https://github.com/Delego-Dev/sample-app/blob/main/SECURITY.md
+    about: Please report security issues privately per our security policy, not as a public issue.

.github/ISSUE_TEMPLATE/feature_request.md

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+---
+name: Feature request
+about: Suggest an idea or improvement
+title: ''
+labels: enhancement
+assignees: ''
+---
+
+## Problem
+<!-- What are you trying to do, and what's missing or hard today? -->
+
+## Proposed solution
+
+## Alternatives considered
+
+## Additional context

.github/PULL_REQUEST_TEMPLATE.md

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+<!-- Fork the repo and open this PR from a branch in your fork. See CONTRIBUTING.md. -->
+
+## What & why
+
+<!-- What does this change do, and why? Link any issue. -->
+
+## AI assistance disclosure (required)
+
+<!-- AI-assisted PRs are welcome but get stricter review. Be specific. -->
+
+- [ ] No AI assistance.
+- [ ] AI-assisted. Tool(s) and how used: ______
+- [ ] AI-generated, human-reviewed. I have read every line and am accountable for it.
+
+## Checklist
+
+- [ ] Forked the repo; this PR comes from a branch in my fork.
+- [ ] `pytest` passes locally.
+- [ ] `python examples/demo.py` still shows all eight scenarios + tamper detection.
+- [ ] **Tests added/updated** for the behaviour changed (or explained why none are needed).
+- [ ] Updated `README.md` and `CHANGELOG.md` for any behaviour change.
+- [ ] I have **not weakened any design invariant** (see `CONTRIBUTING.md` / `ARCHITECTURE.md`):
+  no LLM in the authorization path; no credential custody; fail-closed; approvals
+  bound to fingerprint + intent and single-use; append-only signed audit chain;
+  fixed evaluation order.
+
+## Protocol / spec impact
+
+- [ ] No normative/protocol behaviour changed.
+- [ ] Normative behaviour changed — the [wire spec](https://github.com/Delego-Dev/specification)
+  and its CTK vectors are updated (or a linked spec PR does so), and
+  `__protocol_version__` stays ≤ the spec version.

CODE_OF_CONDUCT.md

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+# Code of Conduct
+
+This project adopts the [Contributor Covenant](https://www.contributor-covenant.org/),
+version 2.1.
+
+We pledge to make participation in our community a harassment-free experience for
+everyone. We are committed to acting and interacting in ways that contribute to
+an open, welcoming, diverse, inclusive, and healthy community.
+
+Examples of behavior that contributes to a positive environment include showing
+empathy and kindness, being respectful of differing opinions, giving and
+gracefully accepting constructive feedback, and focusing on what is best for the
+community. Harassment, insulting or derogatory comments, and other unprofessional
+conduct are not tolerated.
+
+## Reporting
+
+Report unacceptable behavior to **koishore@gmail.com**. All complaints will be
+reviewed and investigated promptly and fairly.
+
+The full text of the Contributor Covenant 2.1 is available at
+<https://www.contributor-covenant.org/version/2/1/code_of_conduct/>.