Add tailored GitHub issue forms

[pppolf]

Summary

• add a focused bug report form for Prayu versions, product surfaces, operating systems, deterministic reproduction, and sanitized diagnostics
• add a feature request form with explicit acceptance criteria and authority/trust-boundary review
• disable blank issues and route questions to Discussions and sensitive reports to the repository Security page

Why

The repository currently has no structured issue intake. These forms make incoming reports more actionable while reinforcing Prayu's privacy and Go-owned authority boundaries. The change is independently valid against main and does not rely on a separate security-policy pull request.

User and developer impact

Contributors get two concise, task-specific forms instead of an unstructured issue. Maintainers receive the environment and boundary information needed to reproduce bugs and evaluate feature proposals without encouraging disclosure of credentials, private prompts, provider payloads, raw tool data, or sensitive local paths.

Validation

• Ruby Psych parsed all three YAML files successfully
• custom basic Issue Form/config schema checks passed (required keys, supported body types, unique IDs, labels, contact-link shape)
• git diff --cached --check
• verified existing bug and enhancement labels
• verified Discussions is enabled and the repository Security route is the independent sensitive-report entry point

Audit

• no credentials or runtime data included
• no product behavior, execution permission, schema, API, or persistence changes
• templates explicitly preserve Prayu's scope, policy, approval, budget, lease, and process-gate model