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

include/core/irq.h

@@ -51,6 +51,13 @@ typedef void (*irq_handler_t)(void *arg);
 #define IRQ_LEVEL_HIGH  2
 #define IRQ_EDGE_LOW    3
 #define IRQ_IS_LEVEL(m) ((m) == IRQ_LEVEL_LOW || (m) == IRQ_LEVEL_HIGH)
+// OR'd into the mode by a handler whose line is *meant* to be silent: the
+// ACPI SCI fires for a power button or a lid, and on a desktop that is never.
+// Without it the poller below took two seconds of silence as a misrouted line
+// and called the handler every tick for the rest of the boot. A line is only
+// exempt while every handler on it says so -- a PCI device sharing the SCI's
+// pin still gets polled.
+#define IRQ_QUIET       0x10
 int  irq_register(int irq, irq_handler_t fn, void *arg, const char *name,
                   int level_low);
 void irq_unregister(int irq, irq_handler_t fn, void *arg);