[add] documentation to explain why the audio tool is excluded.

Author: vmarcella

.github/workflows/release.yml

@@ -62,13 +62,18 @@ jobs:
       - name: Clippy
         run: |
           cargo clippy --workspace \
+            # Excluded in the release workflow to avoid pulling in Linux ALSA
+            # build dependencies (`alsa-sys`) that are unnecessary for release
+            # binaries. Audio/tool validation runs in the CI build matrix when
+            # audio features are enabled.
             --exclude lambda-audio-tool \
             --all-targets \
             -- -D warnings
 
       - name: Tests
         run: |
           cargo test --workspace \
+            # See note above in the Clippy step.
             --exclude lambda-audio-tool \
             -- --nocapture
 
@@ -228,6 +233,9 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
+          # See note in the validate job: `lambda-audio-tool` is excluded here
+          # to avoid Linux ALSA build dependencies that are unnecessary for
+          # release artifacts.
           cargo build --workspace --exclude lambda-audio-tool --release --bins
 
       - name: Stage files