host: process table, shell, coreutils and harness (T8, T9)

T8: sausage:process WIT (spawn, wait, kill), one store per process over the
shared root, /proc/processes, /run, pipeline and cancellation groups, Exec.
brush and 78 uutils commands; the shared cwd-init object sets the cwd from PWD
and keeps numeric exit codes. The corpus matches native bash.

T9: V8 (deno_core) runs pi-durable, pi-ai and chord; SQLite storage in
<dir>/host/harness.sqlite (WAL, synchronous=FULL); file tools on the VFS, bash
through Exec; resumes after SIGKILL.

host/wit/process.wit

@@ -0,0 +1,29 @@
+package sausage:process@0.1.0;
+
+/// Programs share one world. These resources provide lifecycle and bounded stdio transport.
+interface host {
+    use wasi:io/streams@0.2.12.{input-stream, output-stream};
+    record request {
+        program: string,
+        argv: list<string>,
+        env: list<tuple<string, string>>,
+        cwd: string,
+        /// None inherits the parent's group. Zero creates a group. A nonzero ID joins a group.
+        group: option<u32>,
+    }
+    resource child {
+        pid: func() -> u32;
+        group: func() -> u32;
+        stdin: func() -> output-stream;
+        stdout: func() -> input-stream;
+        stderr: func() -> input-stream;
+        status: func() -> option<s32>;
+        wait: func() -> s32;
+        kill: func();
+    }
+    spawn: func(request: request) -> result<child, string>;
+    kill: func(pid: u32) -> result<_, string>;
+}
+world program {
+    import host;
+}