fix: Use nightly with WASI fixes

rust-lang/rust#147572 switched from WASI
specific code in the Rust source to using WASI libc.

The following fixes were required and have been merged into nightly:
* [fix: WASI threading regression by disabling pthread
  usage](rust-lang/rust#151016)
* [Fix std::fs::copy on WASI by setting proper OpenOptions
  flags](rust-lang/rust#150881)

Author: cdmurph32

.github/workflows/tier-1a.yml

@@ -447,7 +447,7 @@ jobs:
       - name: Install Rust toolchain
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: nightly-2025-12-06
+          toolchain: nightly-2026-01-16
 
       - name: Install wasmtime
         run: |
@@ -460,7 +460,7 @@ jobs:
           sudo apt-get install -y clang
 
       - name: Add wasm32-wasip2 target
-        run: rustup target add --toolchain nightly-2025-12-06 wasm32-wasip2
+        run: rustup target add --toolchain nightly-2026-01-16 wasm32-wasip2
 
       - name: Cache Rust dependencies
         uses: Swatinem/rust-cache@v2
@@ -472,7 +472,7 @@ jobs:
           RUST_MIN_STACK: 16777216
           FEATURES: ${{needs.get-features.outputs.rust-native-features}}
         run: |
-          cargo +nightly-2025-12-06 test --target wasm32-wasip2 -p c2pa --features "$FEATURES" --no-default-features -- --no-capture
+          cargo +nightly-2026-01-16 test --target wasm32-wasip2 -p c2pa --features "$FEATURES" --no-default-features -- --no-capture
 
   clippy_check:
     name: Clippy
@@ -524,11 +524,11 @@ jobs:
       - name: Install nightly toolchain
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: nightly-2025-12-06
+          toolchain: nightly-2026-01-16
           components: rustfmt
 
       - name: Check format
-        run: cargo +nightly-2025-12-06 fmt --all -- --check
+        run: cargo +nightly-2026-01-16 fmt --all -- --check
 
   cargo-deny:
     name: License / vulnerability audit