- Add try_idle_context() to ContextSwitchPercpu (switch.rs)
Cross-CPU paths (steal_work, migrate_one_context) use try_idle_context()
instead of idle_context() to avoid panic when APs haven't called
context::init() yet. Returns Option<context::Arc> instead of panicking.
- Pin rust-toolchain.toml to nightly-2026-04-11
- Remove build artifacts (kernel, kernel.all, kernel.sym) from git tracking
- This fixes the boot panic that occurred during multi-CPU scheduling