refactor(process): extract reusable provider lifecycle primitives
Introduce provider-neutral ownership, private runtime roots, absolute startup deadlines, pending-operation correlation, bounded output capture, and verified TERM-to-KILL process supervision.\n\nMigrate Hopper onto the shared lifecycle pieces while keeping its Unix-socket protocol and health/shutdown parsing adapter-specific. Preserve exact ownership checks and fail-closed cleanup, including descendant cleanup after the launcher leader exits.\n\nAdd reusable process fixtures and deterministic coverage for startup timeout, cancellation, output bounds, exit diagnostics, cleanup escalation, repeated close, spawn failure, and resource disposal. Update architecture, provider evaluation, contributor guidance, and generated API documentation.
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