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, 10 insertions, 0 deletions

diff --git a/c/kill.c b/c/kill.c
new file mode 100644
index 0000000..e524627
--- /dev/null
+++ b/c/kill.c
@@ -0,0 +1,10 @@
+#include "gbos.h"
+/* kill <pid>: terminate a process (pid 1 is immortal). */
+void main(void) {
+    char *argv[4];
+    unsigned char argc = argv_parse(argv, 4);
+    unsigned char pid;
+    if (argc < 1) { puts("usage: kill <pid>"); nl(); return; }
+    pid = atou(argv[0]);
+    if (kill(pid)) { puts("kill: no such pid (or immortal)"); nl(); }
+}