docs(host): prove the last 3 files + crate-root deny (unsafe-proof program 4/N, final)

Completes the unsafe-proof program now that the parallel WIP has landed:

- idd_push.rs (25 sites), nvenc.rs (7), punktfunk1.rs (21): a SAFETY proof on
  every unsafe block — D3D11/DXGI COM (same-device textures, immediate-context
  single-thread, keyed-mutex-held convert), the NVENC SDK table (versioned POD,
  register/map/lock-bitstream pairing), cross-process shm reads (atomic
  magic/generation handshake), and the C-ABI harness (each call cross-checked
  against its abi.rs `# Safety` doc). No SUSPECT (UB) blocks.
- capture.rs / encode.rs: the parent-module deny is restored (their WIP children
  are now proven), and main.rs gains a crate-root
  #![deny(clippy::undocumented_unsafe_blocks)] — the permanent catch-all gate so
  no future unsafe block anywhere in the crate can land without a proof.
- Fixed 4 blocks the agents missed: unsafe blocks nested inside `assert_eq!(...)`
  macro args (the comment-above-statement didn't associate) — hoisted to a `let`.
- rustfmt-canonicalized the Windows files (the agents' SAFETY comments + some
  pre-existing 1.9.0 drift) so `cargo fmt --all --check` is clean.

Verified: cargo clippy -p punktfunk-host --all-targets -- -D warnings AND
cargo fmt -p punktfunk-host --check both green with the crate-root deny active.
Windows cfg(windows) re-verified on the box next.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/main.rs

@@ -13,6 +13,10 @@
 
 // Scaffold: trait methods and config paths are defined ahead of their backends.
 #![allow(dead_code)]
+// Unsafe-proof program: every `unsafe {}` / `unsafe impl` in the crate must carry a `// SAFETY:`
+// proof of why it is sound. This crate-root deny is the permanent, catch-all gate (it also covers
+// any future module); individual files keep their own `#![deny(...)]` as belt-and-suspenders.
+#![deny(clippy::undocumented_unsafe_blocks)]
 
 mod audio;
 mod capture;