Separate Music Studio through Pack SDK

[0YHR0]

What changed

• introduce a versioned CompanyTemplateDefinition SDK and deterministic PackCatalog
• move the Music Studio manifest and configuration validation into agentmesh.packs.music_studio
• make generic template preview, install, upgrade preview, and upgrade accept a definition contract
• resolve Music Studio through the built-in catalog while preserving existing HTTP routes
• retain agentmesh.templates.music_studio as a compatibility import
• document the phase-1 scenario boundary and remaining extraction work

Why

AgentMesh core should own execution, governance, persistence, and Pack lifecycle while business scenarios own their vocabulary, manifest, configuration, workflows, and UI. This is the first low-risk boundary before any physical repository split.

User and developer impact

Existing Music Studio API clients and legacy Python imports continue to work. New scenarios can implement the SDK contract and register in a catalog without adding scenario validation to CompanyPackService.

Validation

• Ruff passed
• JavaScript syntax check passed
• 418 tests passed, 28 PostgreSQL-gated tests skipped locally
• 83.09% line coverage, above the 80% gate