feat(release): build static Linux x64 binaries with musl

Switch Linux x64 release builds from dynamic glibc (x86_64-unknown-linux-gnu)
to static musl (x86_64-unknown-linux-musl) in GitHub Actions release workflow.

- Change matrix target for codewhale and codewhale-tui linux-x64 to musl
- Add dedicated musl build step: install musl-tools, add musl target
- Skip libdbus-1-dev install for musl targets (keyring gated at compile time)
- Skip generic Build step for musl (handled by dedicated step)
- Parity with CNB pipeline (.cnb.yml) which already uses musl (PR #2903)

Static binaries have no glibc/libdbus runtime dependency and run on any
Linux distribution without additional packages.

.github/workflows/release.yml

@@ -27,7 +27,7 @@ jobs:
         with:
           components: clippy, rustfmt
       - name: Install Linux system dependencies
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && matrix.target != 'x86_64-unknown-linux-musl'
         run: |
           for i in 1 2 3 4 5; do
             sudo apt-get update && break
@@ -111,7 +111,7 @@ jobs:
         include:
           # --- codewhale (cli dispatcher, canonical) ---
           - os: ubuntu-latest
-            target: x86_64-unknown-linux-gnu
+            target: x86_64-unknown-linux-musl
             binary: codewhale
             artifact_name: codewhale-linux-x64
           - os: ubuntu-latest
@@ -136,7 +136,7 @@ jobs:
             artifact_name: codewhale-windows-x64.exe
           # --- codewhale-tui (TUI runtime, canonical) ---
           - os: ubuntu-latest
-            target: x86_64-unknown-linux-gnu
+            target: x86_64-unknown-linux-musl
             binary: codewhale-tui
             artifact_name: codewhale-tui-linux-x64
           - os: ubuntu-latest
@@ -171,7 +171,7 @@ jobs:
         with:
           cache-bin: false
       - name: Install Linux system dependencies
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && matrix.target != 'x86_64-unknown-linux-musl'
         run: |
           for i in 1 2 3 4 5; do
             sudo apt-get update && break
@@ -179,6 +179,14 @@ jobs:
             sleep 15
           done
           sudo apt-get install -y libdbus-1-dev pkg-config
+      - name: Build static Linux x64 binary (musl)
+        if: matrix.target == 'x86_64-unknown-linux-musl'
+        shell: bash
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y musl-tools
+          rustup target add x86_64-unknown-linux-musl
+          cargo build --release --locked --target x86_64-unknown-linux-musl
       - name: Install RISC-V cross-compilation toolchain
         if: matrix.target == 'riscv64gc-unknown-linux-gnu'
         run: |
@@ -215,6 +223,7 @@ jobs:
           sudo apt-get update -o Dir::Etc::sourcelist=/etc/apt/sources.list.d/arm64.sources -o Dir::Etc::sourceparts=- -o APT::Get::List-Cleanup=0
           sudo apt-get install -y gcc-aarch64-linux-gnu libc6-dev-arm64-cross libdbus-1-dev:arm64 pkg-config
       - name: Build
+        if: matrix.target != 'x86_64-unknown-linux-musl'
         shell: bash
         env:
           DEEPSEEK_BUILD_SHA: ${{ needs.resolve.outputs.sha }}