Process and connection isolation

A namespace is never a process identity. ProcessKey binds the reviewed server configuration, exact executable identity, MCP revision, tenant security partition, upstream credential identity, environment digest, shareability class, and—where required—principal or unique instance partition.

Unknown servers default to NON_SHAREABLE. Principal-isolated entries require a principal partition; non-shareable entries require an instance nonce. The pool has a hard semaphore bound, reference counts, startup/shutdown/idle limits, and a finite restart budget with generation tracking. RMCP spawns stdio with an exact executable plus argument array; no shell is involved and the child transport is cancelled after use.

The current pool core deliberately does not claim production child-tree containment on Windows. Platform job objects/process groups, stderr and framing caps, idle reaping, and fault-injected orphan tests remain release gates. The stdio integration test does verify that GaugeMesh owns, cancels, and joins the direct child it starts.