feat: build system hardening — unwired patch detector + rebrand

check-unwired-patches.sh: scans local/patches/ for .patch files not
referenced in any recipe.toml patches = [...] array. Detects 262
unwired patches (most intentionally kept for reference/rebase).

P2-rebrand-start-message.patch: minimal 39-line patch changing
'Redox OS starting' to 'RedBear OS starting' in x86_64, aarch64,
and riscv64 arch start files. Wired into kernel recipe after
P8-msi.patch. Verified: make r.kernel builds with all 3 patches.

Build system issues surfaced by the detector:
- 250+ kernel individual patches kept for reference (absorbed/)
- ~50 base individual patches — many intentionally unwired
- ~30 relibc patches — may need wiring into relibc recipe
- build-system patches applied by scripts, not recipes

local/patches/kernel/P2-rebrand-start-message.patch

@@ -0,0 +1,39 @@
+diff --git a/src/arch/aarch64/start.rs b/src/arch/aarch64/start.rs
+index e1c8cfb4..65e3fe33 100644
+--- a/src/arch/aarch64/start.rs
++++ b/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
+diff --git a/src/arch/riscv64/start.rs b/src/arch/riscv64/start.rs
+index 2551968f..a825536a 100644
+--- a/src/arch/riscv64/start.rs
++++ b/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 {
+diff --git a/src/arch/x86_shared/start.rs b/src/arch/x86_shared/start.rs
+index 7a7c0ae8..62f9523c 100644
+--- a/src/arch/x86_shared/start.rs
++++ b/src/arch/x86_shared/start.rs
+@@ -91,7 +91,7 @@ unsafe extern "C" fn start(args_ptr: *const KernelArgs, stack_end: usize) -> ! {
+             // Set up graphical debug
+             graphical_debug::init(args.env());
+ 
+-            info!("Redox OS starting...");
++            info!("RedBear OS starting...");
+             args.print();
+ 
+             // Set up GDT