kill + ps: implement SYS_KILL (pid 1 immortal) and a ps tool

- PCB gains PROC_PROG (running program id), set by exec, inherited on fork.
- sys_kill(pid): reject pid 1 (immortal) and unknown/dead pids; mark the target
  zombie, reparent its children to init, wake its parent if blocked in wait;
  schedule away if a process kills itself. Reuses FindPcbByPid/ReparentToInit.
- sys_ps(slot,buf)->{pid,state,prog}; sys_progname(id) via NameTable reverse
  lookup. NameTable gains sh/ps/kill.
- libc: kill/psget/progname; tools ps (pid state cmd) and kill <pid>.
- verified: ps lists sh(B)+ps(R); kill 1 refused; kill 42 fails.

1 files changed, 14 insertions, 0 deletions

diff --git a/c/ps.c b/c/ps.c
new file mode 100644
index 0000000..7bfc0de
--- /dev/null
+++ b/c/ps.c
@@ -0,0 +1,14 @@
+#include "gbos.h"
+/* ps: list live processes (pid, state, command). */
+void main(void) {
+    unsigned char i, buf[3];
+    char name[9];
+    for (i = 0; i < 8; i++) {
+        if (psget(i, buf)) {              /* buf = {pid, state, prog} */
+            putu(buf[0]); putc(' ');
+            putc("-RrBZ"[buf[1]]); putc(' ');
+            progname(buf[2], name);
+            puts(name); nl();
+        }
+    }
+}