Add repository contribution templates

[DavidBakerEffendi]

Description

Add Mjolnir-specific community health files based on the structure used by Anvil and Bifrost. The new forms distinguish runtime/UI reports from installation and release problems, while the contributor guidance documents the repository's current terminal, ACP, Council, voice-worker, licensing, review, and release practices.

Key Changes:

• Add focused TUI/session/remote and other-bug issue forms, a feature-request form, blank-issue support, and Mjolnir documentation/community links.
• Add a pull request template that asks for semantic changes, affected-surface evidence, terminal and Council conditions, capability boundaries, visual evidence, and exact validation.
• Add an AI-friendly Code of Conduct and a contributor guide grounded in Mjolnir's current build, test, UI-safety, dependency-license, review, and tag-release workflows.

Touch Points:

• .github/ISSUE_TEMPLATE/
• .github/pull_request_template.md
• CODE_OF_CONDUCT.md
• CONTRIBUTING.md

Validation:

• Parsed every issue form and chooser config as YAML; checked required structure, unique field IDs, live labels, and blank-issue configuration.
• Verified all local Markdown links and checked for trailing whitespace.
• git diff --cached --check
• cargo fmt --check
• Rust tests were not run because this change contains only GitHub metadata and Markdown documentation.