bug pass: whole console lines, a quiet SCI, an honest reserve warning

- schinit, schinitd and vgpud build every message from pieces, one
  write() each, so a job starting on another CPU landed mid-line:
  "schinitd: starting vgpud: os.schos.resolvconfno virtio-gpu on this
  machine". They now collect a line and write it at the newline;
  resolvconf's verbose line is one write with its prefix.
- The ACPI SCI registers IRQ_QUIET. A desktop's SCI never fires, and the
  poller took two seconds of silence for a misrouted line ("irq 9:
  nothing has arrived on it") and called the handler every tick. A line
  is only exempt while every handler on it is quiet.
- The loader claims each segment from where the last one's claim ended,
  so two segments sharing a page no longer ask for it twice. When a
  claim is still refused, it names the memory-map entries in the way.
- Stale divesymlink() declaration gone; the kernel.md struct table
  re-measured (inode, buf and file pools grow from slabs now).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

cmd/schinit/main.c

@@ -119,10 +119,34 @@ read_bootmode(void)
     if (n > 0) { b[n] = 0; verbose_boot = (b[0] == 'v'); }
 }
 
+// Whole lines, in one write() each: the same buffer as schinitd's, for the
+// same reason -- a line written in pieces is a line another process can land
+// in the middle of. See emit() there.
+static char lbuf[512];
+static int  lbn;
+
+static void
+lflush(void)
+{
+    if (lbn)
+        write(1, lbuf, lbn);
+    lbn = 0;
+}
+
+static void
+emit(const char *s, int n)
+{
+    for (int i = 0; i < n; i++) {
+        lbuf[lbn++] = s[i];
+        if (s[i] == '\n' || lbn == (int)sizeof lbuf)
+            lflush();
+    }
+}
+
 static void
 out(const char *s)
 {
-    write(1, (void *)s, slen(s));
+    emit(s, slen(s));
 }
 
 static void
@@ -410,6 +434,7 @@ spawn(struct schinit_spawn *s)
         out("schinit: cannot exec ");
         out(s->program);
         out("\n");
+        lflush();
         exit();
     }
     return pid;