v0.5.5: visible boot progress + panic-on-screen for real hardware

Real hardware has no serial console: a pre-shell panic was a silent
blank screen (the panic handler only wrote to serial, then cli;hlt).
v0.5.4's shadow change made this window reachable — if the fb-aware
page allocation or the heap fallback failed on hardware, the kernel
halted before the shell banner with zero screen output.

- gop::boot_marker(): every boot stage now draws straight to the
  framebuffer (row 0, white-on-black).  The last marker visible before
  a hang identifies where the kernel died.
- Panic handler: pre-shell panics now draw a white-on-red
  '*** PANIC *** <msg> at file:line' band via gop::dump_lines.
- init_shadow(): heap fallback is panic-proof (try_reserve_exact +
  resize instead of vec![0; words] which aborts on OOM); page-alloc
  result defensively re-checked against the fb region; any failure
  degrades to no-shadow mode with a visible warning band.
- Verified: full chain (rsboot -> kernel) boots with markers, shell
  banner renders, all 5 test suites pass.

1 files changed, 3 insertions, 3 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 2796caa..431db32 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,7 +4,7 @@ version = 4
 
 [[package]]
 name = "rsdos"
-version = "0.5.4"
+version = "0.5.5"
 dependencies = [
  "rsnix",
  "shell",
@@ -19,11 +19,11 @@ dependencies = [
 
 [[package]]
 name = "rsnix"
-version = "0.5.4"
+version = "0.5.5"
 
 [[package]]
 name = "shell"
-version = "0.5.4"
+version = "0.5.5"
 dependencies = [
  "rsdosedit",
  "rsnix",