[plan] Review and address template injection warnings

[github-actions]

Objective

Review the 5 template injection warnings identified by zizmor and implement appropriate input sanitization where needed.

Context

Priority: 🔵 Priority 4 (Low/Informational security warnings)

While these are marked as Informational/Low severity, template injection vulnerabilities should be reviewed to ensure proper input sanitization in GitHub expressions.

Affected Workflows

1. breaking-change-checker.md - Line 5781:9 (Informational)

   • Step: "Assign copilot to created issues"

2. changeset.md - Line 6254:9 (Informational)

   • Step: "Configure Git credentials"

3. duplicate-code-detector.md - Line 5668:9 (Informational)

   • Step: "Assign copilot to created issues"

4. mcp-inspector.md - Line 1784:9 (Low)

   • Step: "Setup MCPs"

5. release.md - Line 461:9 (Informational)

   • Step: "Setup environment and fetch release data"

Reference: (redacted)#template-injection

Approach

For each workflow:

1. Identify the GitHub expression that triggered the warning
2. Determine if untrusted user input is being used in the expression
3. If yes, implement one of these mitigations:
   • Use environment variables with ${{ env.VAR }} instead of direct injection
   • Use github.event.*.id (numeric IDs) instead of text fields
   • Sanitize inputs before use
4. If the expression only uses trusted GitHub context, document why it's safe

Files to Review

• .github/workflows/breaking-change-checker.md (line ~5781)
• .github/workflows/changeset.md (line ~6254)
• .github/workflows/duplicate-code-detector.md (line ~5668)
• .github/workflows/mcp-inspector.md (line ~1784)
• .github/workflows/release.md (line ~461)

Acceptance Criteria

• All 5 template injection warnings reviewed
• Mitigation applied or safety documented for each case
• Zizmor scan shows reduced warnings (or documented acceptance)
• No functional regressions in affected workflows
• Security review notes documented in commit message

Testing

# Re-run zizmor scan on all affected workflows
gh aw compile breaking-change-checker --zizmor
gh aw compile changeset --zizmor
gh aw compile duplicate-code-detector --zizmor
gh aw compile mcp-inspector --zizmor
gh aw compile release --zizmor

Related to #5294

AI generated by Plan Command for discussion #5280