feat: consolidate runtime, work, and composer foundations

[GCWing]

Summary

• extract shared relay and tool-runtime crates, simplify transport/event boundaries, and add architecture enforcement
• establish durable Work, Composer submission, and Product App lifecycle contracts across Core, desktop, CLI, and Web UI
• unify Composer context handling, auxiliary scene focus, Product App runtime state, and the panel icon system
• harden PPT Live and Remotion Live runtime behavior while removing duplicate or retired editable Product App bundles

Scope exclusions

The PR intentionally excludes Logo explorations, standalone product/design documents, QA screenshots, preview artifacts, local caches, and the Windows NUL stray file. Product App agent prompts and skill files remain included because they are executable runtime assets.

Validation

• cargo fmt --all -- --check
• cargo check --workspace --exclude sparo-cli
• cargo check -p sparo-cli --tests
• Web UI TypeScript check
• 14 focused Web UI test files: 71 tests passed
• focused PPT Live and Remotion Live tests: 36 tests passed
• architecture gate: 105 tracked baseline violations, 0 new
• i18n consistency check
• design-system architecture check
• icon generation and TypeScript check
• clean committed-tree brand residue check
• staged diff whitespace check

Full Tauri E2E was not run.