chore: gitignore target-linux/ cross-build cache (two cache files slipped into #1397) (#1398)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -73,3 +73,6 @@ assets/generate-waitlist.py
 
 # Local scratch tests (never commit)
 __tests__/zz-scratch*
+
+# linux-arm64 kernel cross-build cache (rust:1-bookworm builder)
+target-linux/

target-linux/.rustc_info.json

@@ -1 +0,0 @@
-{"rustc_fingerprint":4293921394394104691,"outputs":{"7971740275564407648":{"success":true,"status":"","code":0,"stdout":"___\nlib___.rlib\nlib___.so\nlib___.so\nlib___.a\nlib___.so\n/usr/local/rustup/toolchains/1.97.1-aarch64-unknown-linux-gnu\noff\npacked\nunpacked\n___\ndebug_assertions\npanic=\"unwind\"\nproc_macro\ntarget_abi=\"\"\ntarget_arch=\"aarch64\"\ntarget_endian=\"little\"\ntarget_env=\"gnu\"\ntarget_family=\"unix\"\ntarget_feature=\"neon\"\ntarget_has_atomic=\"128\"\ntarget_has_atomic=\"16\"\ntarget_has_atomic=\"32\"\ntarget_has_atomic=\"64\"\ntarget_has_atomic=\"8\"\ntarget_has_atomic=\"ptr\"\ntarget_has_atomic_primitive_alignment=\"128\"\ntarget_has_atomic_primitive_alignment=\"16\"\ntarget_has_atomic_primitive_alignment=\"32\"\ntarget_has_atomic_primitive_alignment=\"64\"\ntarget_has_atomic_primitive_alignment=\"8\"\ntarget_has_atomic_primitive_alignment=\"ptr\"\ntarget_os=\"linux\"\ntarget_pointer_width=\"64\"\ntarget_vendor=\"unknown\"\nunix\n","stderr":""},"4054631422912855907":{"success":true,"status":"","code":0,"stdout":"rustc 1.97.1 (8bab26f4f 2026-07-14)\nbinary: rustc\ncommit-hash: 8bab26f4f68e0e26f0bb7960be334d5b520ea452\ncommit-date: 2026-07-14\nhost: aarch64-unknown-linux-gnu\nrelease: 1.97.1\nLLVM version: 22.1.6\n","stderr":""}},"successes":{}}

target-linux/CACHEDIR.TAG

@@ -1,3 +0,0 @@
-Signature: 8a477f597d28d172789f06886806bc55
-# This file is a cache directory tag created by cargo.
-# For information about cache directory tags see https://bford.info/cachedir/