feat: add GitHub Copilot prompt support

Adds GitHub Copilot VS Code instruction and prompt files for ECC workflows, with VS Code prompt frontmatter/settings aligned to current docs and tests covering the surface.

Co-authored-by: Girish Kanjiyani <girish.kanjiyani5040@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/prompts/security-review.prompt.md

@@ -0,0 +1,70 @@
+---
+agent: agent
+description: Deep security analysis — OWASP Top 10, secrets, auth, injection, and dependency risks
+---
+
+# Security Review
+
+Perform a thorough security analysis of the selected code or current branch changes.
+
+## Checklist
+
+### Secrets & Configuration
+- [ ] No hardcoded API keys, tokens, passwords, or private keys anywhere in source
+- [ ] All secrets loaded from environment variables or a secret manager
+- [ ] Required env vars validated at startup (fail fast if missing)
+- [ ] `.env` files excluded from version control
+
+### Input Validation & Injection
+- [ ] All user inputs validated and sanitized before use
+- [ ] Parameterized queries for every database operation (no string interpolation)
+- [ ] HTML output escaped or sanitized (XSS prevention)
+- [ ] File path inputs sanitized (path traversal prevention)
+- [ ] Command inputs sanitized (command injection prevention)
+
+### Authentication & Authorization
+- [ ] Auth checks enforced server-side — never trust client-supplied user IDs or roles
+- [ ] Session tokens are sufficiently random and expire appropriately
+- [ ] Sensitive operations protected by authz checks, not just authn
+- [ ] CSRF protection enabled for state-changing endpoints
+
+### Data Exposure
+- [ ] Error responses scrubbed of stack traces, internal paths, and sensitive data
+- [ ] Logs do not contain PII, tokens, or passwords
+- [ ] Sensitive fields excluded from API responses (no over-fetching)
+- [ ] Appropriate HTTP security headers set
+
+### Dependencies
+- [ ] No known vulnerable packages (run `npm audit` / `pip-audit` / `cargo audit`)
+- [ ] Dependency versions pinned or locked
+- [ ] No unused dependencies that increase attack surface
+
+### Infrastructure (if applicable)
+- [ ] Rate limiting on all public endpoints
+- [ ] HTTPS enforced; no HTTP fallback in production
+- [ ] Principle of least privilege for service accounts and IAM roles
+
+## Response Protocol
+
+If a **CRITICAL** issue is found:
+1. Stop and report immediately.
+2. Do not ship until fixed.
+3. Rotate any exposed secrets.
+4. Scan the rest of the codebase for similar patterns.
+
+## Output Format
+
+```
+## Findings
+
+**[CRITICAL|HIGH|MEDIUM|LOW]** — [category]
+Location: [file:line if known]
+Issue: [what is wrong and why it is dangerous]
+Fix: [concrete remediation]
+
+## Summary
+- Critical: N
+- High: N
+- Medium: N
+- Safe to ship: yes / no
+```