Merge #2151: fix(ci): pin toolchain, and switch to actions-rust-lang/setup-rust-toolchain

c99a547 fix(ci): pin toolchain, and switch to `actions-rust-lang/setup-rust-toolchain` (valued mammal)

Pull request description:

  ### Description

  Currently the code coverage step is failing on `release/chain-0.23.x`, this PR applies the fix that's currently in master.

  ### Changelog notice

  ```
  ### Changed

  - ci(coverage): switch to `action-rust-lang/setup-rust-toolchain`.
  - ci(coverage): pin toolchain to `nightly-2025-11-27`.

  ```

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

  #### Bugfixes:

  * [x] This pull request breaks the existing API
  * [x] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  luisschwab:
    ACK c99a547

Tree-SHA512: bf7d28fc243d6248736a5db8416bc128aeb0bf9be14360105f013e732d0a6a6113dc46a017d09655e56a46c0d485552392c554535fe3efddddf83b4b0593a631

Author: oleonardolima

.github/workflows/code_coverage.yml

@@ -16,20 +16,18 @@ jobs:
       - name: Install lcov tools
         run: sudo apt-get install lcov -y
       - name: Install Rust toolchain
-        uses: actions-rs/toolchain@v1
+        uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
-            toolchain: nightly
+            toolchain: nightly-2025-11-27
             override: true
-            profile: minimal
+            cache: true
             components: llvm-tools-preview
-      - name: Rust Cache
-        uses: Swatinem/rust-cache@v2.7.8
       - name: Install cargo-llvm-cov
         run: if [[ ! -e ~/.cargo/bin/cargo-llvm-cov ]]; then cargo install cargo-llvm-cov; fi
       - name: Make coverage directory
         run: mkdir coverage
       - name: Test and report coverage
-        run: cargo +nightly llvm-cov -q --doctests --branch --all --ignore-filename-regex "(example*|crates/testenv/*)" --all-features --lcov --output-path ./coverage/lcov.info
+        run: cargo llvm-cov -q --doctests --branch --all --ignore-filename-regex "(example*|crates/testenv/*)" --all-features --lcov --output-path ./coverage/lcov.info
       - name: Generate HTML coverage report
         run: genhtml -o coverage-report.html --ignore-errors unmapped ./coverage/lcov.info
       - name: Coveralls upload

.github/zizmor.yml

@@ -0,0 +1,7 @@
+# Zizmor config
+rules:
+  unpinned-uses:
+    config:
+      policies:
+        # Allow pin by ref/tag
+        actions-rust-lang/setup-rust-toolchain: ref-pin