feat: publish Iris container images and self-host docs (COD-425)

[shivros]

Summary

• Publish multi-architecture (linux/amd64, linux/arm64) Iris images to GHCR on v* tags.
• Document a loopback-bound Iris Docker run, including the no-auth private-network warning.
• Add the reference Iris + Rite Compose deployment with persistent Iris data and internal Rite-to-Iris wiring.

Validation

• actionlint .github/workflows/release.yml — pass
• docker compose -f deploy/docker-compose.yml config with placeholder required secrets — pass
• git diff --check — pass
• Rust build/test/clippy gates were not rerun: the host /tmp filesystem was full (ENOSPC) while compiling fresh disposable-worktree targets. This change does not alter Rust sources or generated artifacts.

Live GHCR publishing is intentionally deferred to the first release tag; this PR does not create a tag.

[shivros]

🤖 Automated Review Panel

GPT-5.6-terra

BLOCK (review-context transcription only): the supplied compacted review context represented tags as a single-quoted literal \n, which would be invalid metadata-action input. The actual committed workflows use a YAML block scalar with real line breaks; local actionlint passed both workflows. No remaining material finding against the committed diff.

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Gemini 3 Flash

APPROVE. The tag trigger, least-privilege package publishing permissions, GHCR authentication, multi-architecture build, image tags, loopback-bound self-host commands, no-auth warning, and Iris–Rite Compose wiring align with COD-425. Compose configuration and workflow linting passed.

[shivros]

Auto-Merge Gate

Confidence: 0.91

Rationale: COD-425 clearly requires tag-triggered, multi-architecture GHCR publication, self-host documentation, and a validated Iris + Rite Compose reference. This three-file change implements those requirements directly. The workflow uses the required tag trigger, least-privilege contents: read / packages: write permissions, official Docker actions, QEMU/Buildx, and linux/amd64,linux/arm64. The Compose deployment binds unauthenticated Iris to loopback and wires Rite privately.

Checks observed: CI Test, Format Check, Clippy, Secret Scan, Dependency Audit, and Creed context drift all succeeded. Local git diff --check and Compose configuration validation passed.

Scope limits: No tag, release, live deployment, or live GHCR publishing was performed. First tag-push validation remains a separate acceptance step.