license: GPL-2.0-only repo-wide

Replaces the dual MIT/Apache-2.0 licensing (and its GPL carve-out) with a
single GPL-2.0-only license for the whole repository: coherent with the
kernel patch series it exists to carry, the embedded-Linux norm, and the
stack's openness principle — anyone shipping products on this SDK publishes
their changes. GPL-2.0 (not 3) deliberately: the Installation-Information
clause of GPLv3 sits badly with WardenOS's signed A/B firmware chain.
LICENSE is now the canonical GPLv2 text; crate manifests updated;
inbound = outbound noted in the README.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018HUayid7W5w7jBdb9Rrj1K

tools/config-lint/Cargo.toml

@@ -3,7 +3,7 @@ name = "warden-config-lint"
 version = "0.1.0"
 edition = "2021"
 description = "Static target-config checks for WardenOS: catch memory-map faults (the 0x40000 MCU-load brick class) and other flash-time config mistakes before a flash, not on the bench."
-license = "MIT OR Apache-2.0"
+license = "GPL-2.0-only"
 
 [[bin]]
 name = "config-lint"