kernel: update 'Redox OS starting' -> 'RedBear OS starting' on all architectures

Branding fix across all 3 architectures to match the active Red Bear
identity. Previously the kernel fork's start messages still claimed
'Redox OS starting' on aarch64, riscv64, and x86_shared, while the
canary/debug patches added later correctly used the new branding.

This commit completes the user-facing branding pass: after this, every
Red Bear OS boot logs 'RedBear OS starting...' instead of 'Redox OS
starting...'.

Patches applied:
- kernel/P2-redbear-os-branding: 2 of 3 architecture files automatically
  patched via patch(1) fuzz=5
- kernel/src/arch/x86_shared/start.rs: 1 hunk applied via fuzz=2; the
  remaining 'Redox OS starting' literal updated via direct edit since
  patch context for that line was already canary-disturbed

src/arch/aarch64/start.rs

@@ -91,7 +91,7 @@ unsafe extern "C" fn start(args_ptr: *const KernelArgs) -> ! {
                 dtb::serial::init_early(dtb);
             }
 
-            info!("Redox OS starting...");
+            info!("RedBear OS starting...");
             args.print();
 
             // Initialize RMM

src/arch/riscv64/start.rs

@@ -97,7 +97,7 @@ unsafe extern "C" fn start(args_ptr: *const KernelArgs) -> ! {
                 init_early(dtb);
             }
 
-            info!("Redox OS starting...");
+            info!("RedBear OS starting...");
             args.print();
 
             if let Some(dtb) = &dtb {

src/arch/x86_shared/start.rs

@@ -109,7 +109,7 @@ unsafe extern "C" fn start(args_ptr: *const KernelArgs, stack_end: usize) -> ! {
                 core::arch::asm!("out dx, al", in("dx") 0x3F8u16, in("al") b'S', options(nostack, preserves_flags));
             }
 
-            info!("Redox OS starting...");
+            info!("RedBear OS starting...");
             args.print();
 
             #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]