Reserve Boat SSH capacity for lifecycle and process control

Bound each physical Boat to eight SSH operations with six ordinary slots and four bulk transfers. Preserve command deadlines while queued and always release admission after transport completion or failure.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/modules/computers/application/ports.ts

@@ -31,7 +31,7 @@ export interface ComputerBackend {
   ready(record: ComputerRecord): Promise<void>;
   claim(record: ComputerRecord): Promise<void>;
   advance(record: ComputerRecord, owner: Owner): Promise<void>;
-  runner(record: ComputerRecord): Promise<CommandManagedRuntimeRunner>;
+  runner(record: ComputerRecord, options?: { control?: boolean }): Promise<CommandManagedRuntimeRunner>;
   launch(
     record: ComputerRecord,
     owner: Owner,

server/src/modules/computers/application/service.ts

@@ -170,6 +170,7 @@ export function createComputerService(
     if (!placement)
       throw new ComputerError("conflict", "Computer placement is missing");
     const raw = await backend.runner(record);
+    const control = await backend.runner(record, { control: true });
     let pinnedProcess = owner.process ? structuredClone(owner.process) : null;
     async function processScope() {
       if (!pinnedProcess) return scoped({ ...record, owner: ownerRef });
@@ -203,7 +204,7 @@ export function createComputerService(
           throw new ComputerError("conflict", "Computer owner is retired");
         // Start a command unit under the same owner slice while holding the remote tombstone lock.
         // The lock is released only after systemd knows the unit, so retirement cannot miss a delayed launch.
-        return raw.execute({
+        return (processScoped ? control : raw).execute({
           command: "python3",
           args: [
             "-c",