Style: complete public brand asset kit

[ivory-code]

Summary

• Add a dedicated 1280 x 640 GitHub repository social preview.
• Preserve the remaining editable SVG masters, transparent marks, app icons, favicons, touch icon, and PWA icons in a GitHub-only brand kit.
• Document each production asset and extend repository contracts for dimensions, vector portability, links, and package boundaries.

Behavioral Contract

No runtime QA behavior change. Repository validation now fails when an official brand export has the wrong dimensions, an editable SVG embeds unsupported content, the favicon is invalid, or brand documentation links drift.

Evidence

• The source, PNG, and web directories match the approved local brand package byte for byte.
• docs/assets/qamap-github-social-preview-1280x640.png is an exact 2:1 export of the approved README cover.
• The npm dry run includes the deployed GitHub banner but excludes the GitHub-only source brand kit.
• QAMap routes this change to repository validation and selects the focused contributor workflow test rather than product E2E.

Checks

• Focused regression test
• pnpm test
• pnpm bench:ci for inference, routing, trace, or output
• pnpm bench:execution for E2E compiler or execution fixtures
• pnpm scan for scanner, security, or repository policy
• pnpm plugin:check and pnpm plugin:smoke for plugin changes
• Documentation links and commands verified

Public OSS Check

• No private repository, source, path, customer data, credential, or internal smoke output is included.
• Shared inference has unrelated positive and negative coverage, or this is not applicable.
• User-facing commands and claims match actual behavior.

Review Notes

pnpm bench:ci, pnpm bench:execution, and pnpm scan are N/A because this change does not modify inference, execution, scanner behavior, or repository policy. The GitHub social preview must still be uploaded manually from docs/assets/qamap-github-social-preview-1280x640.png in repository settings.