fix(fmt) + feat(gamepad): CI-matching rustfmt everywhere, enforced by repo git hooks; N4 spike flips to GO via MI_02

Three things that belong together:

1. rustfmt the gamepad-new-types host files ci.yml's `cargo fmt --all
   --check` gate flags (the .21/.133 verify recipes ran clippy+tests
   but never fmt — the same class of miss as 69f30f30).

2. Enforce it at the source: scripts/git-hooks/{pre-commit,pre-push}
   run the exact CI fmt gates (main workspace + the shipped-driver
   crates of the UMDF workspace); CONTRIBUTING documents the one-time
   `git config core.hooksPath scripts/git-hooks`. pre-push is the
   enforcement point (plumbing commits bypass pre-commit).

3. N4 follow-up — the spike verdict FLIPS TO GO: SwDeviceProfile grows
   `usb_mi`, synthesizing `&MI_02` into the Deck spike's USB hardware
   ids. hidclass mirrors the parent's USB tokens into the HID child's
   hardware ids, and hidapi/SDL/Steam parse `MI_` as bInterfaceNumber
   (defaulting to 0 when absent — the exact gate the first run hit:
   Steam wants the Deck controller on interface 2). Re-run live on
   .173: Steam logs `Interface: 2`, then `!! Steam controller device
   opened`, `Steam Controller reserving XInput slot 0`, and activates
   a mapping — full Steam Input promotion of the software-devnode
   Deck, no driver change needed. The PS identities pass
   `usb_mi: None` (real single-interface devices carry no MI_ token).
   A proper Windows-Deck backend phase is now justified; planned
   separately.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CONTRIBUTING.md

@@ -30,6 +30,16 @@ file with `scripts/gen-third-party-notices.sh` when the dependency tree changes.
 
 ## Before you push
 
+Enable the repo git hooks once per clone — they run the exact rustfmt gates CI runs (main
+workspace + the UMDF driver workspace) on every commit and push, so a push can never fail CI
+on formatting alone:
+
+```sh
+git config core.hooksPath scripts/git-hooks
+```
+
+Then the usual full pass:
+
 ```sh
 cargo fmt --all --check
 cargo clippy --workspace --all-targets -- -D warnings