feat(assets): add synthetic schema and compiler

[blakinio]

Purpose

Implement the single authorized W6-ASSET lane from the merged and archived W6 plan.

Delivered scope

• oteryn-asset-types, category asset-types;
• oteryn-asset-compiler, category tool, consuming asset-types;
• typed non-zero IDs, bounded blob/RGBA8 metadata and SHA-256 payload digests;
• original deterministic little-endian pack schema v1 with canonical ordering and strict decoder/validator;
• constrained JSON manifest compiler with checked record/string/payload/pack/dimension limits;
• relative-path, symlink, canonical-containment, regular-file and bounded-read protections;
• same-directory temporary output and final rename without replacing an existing output;
• original synthetic manifest, blob and RGBA8 fixtures with documented provenance;
• generated Cargo lockfile and required workspace/catalogue/test/changelog/evidence documentation.

Final validation

Final head: c51b24c489b181bc8a950a94d1fdf272bc60be7a.

• Rust Client run 30494659925: passed locked metadata, Rust 1.94 formatting, Clippy, all workspace tests, architecture policy and Supply Chain.
• Repository CI run 30494660024: passed.
• Final synchronized diff review: exactly 18 authorized paths.
• No unresolved review threads, requested changes or ownership conflicts.

The formatting-only repair was generated with pinned Rust 1.94. Its temporary workflow was removed and is absent from the final tree and PR diff.

Exact scope

Exactly 18 authorized paths. No final .github/workflows/**, Rust toolchain, architecture-checker source/rules/fixtures, deny.toml, REPOSITORY_LAYOUT.md, legacy runtime or external-repository change.

Safety boundaries

No asset runtime, mounting/streaming/cache, renderer/GPU integration, image/archive/compression stack, real Tibia/Canary importer, proprietary input, updater/download, signing, authenticated manifest, protocol, identity, networking, UI, audio or feature implementation.

Synthetic compiler success does not prove production format compatibility, redistribution rights, real Canary input support, runtime behavior, signing/update security, production limits or performance.

Task

OTC-20260729-synthetic-asset-schema-compiler

[blakinio]

Coordination note: draft PR #93 continues the merged legacy options work and intentionally leaves docs/agents/CHANGELOG.md untouched while this PR holds the active shared-path lease. There is no implementation-path overlap. After this lane merges and archives, #93 will reconcile its narrow changelog entry on current main before readiness.