A1: Parse-100 — fix last 9 non-parsing kernel files

Workstream A milestone A1 (MASTER_PLAN.md §6).

Current: 400/409 (scripts/parse-rate.sh). Target: 409/409, then wired into CI as the parse-rate gate.

Failing files and their Zig-era constructs:

• kernel/src/arch/arm64/rpi/boot.home — extern "C" fn(...) type syntax
• kernel/src/arch/arm64/rpi/devicetree.home — 'static lifetimes, ..= match range patterns
• kernel/src/drivers/platform/laptop.home — Zig array-repeat init [X]{null} ** N
• kernel/src/fs/sparse.home — Zig for (...) else true loop-else expression
• kernel/src/perf/lockfree.home — labeled blocks / goto retry, @bitcast casing
• kernel/src/power/battery.home — tuple patterns in if let
• kernel/src/power/cpu_state.home — C preprocessor #if defined(...)
• kernel/src/security/dm_verity.home — full Zig file (std.heap, defer, labeled switch)
• kernel/src/security/module_signing.home — Zig blk: labeled block breaks in switch

Part of #21.