ci: musl toolchain references 15.1.0 -> 16.1.0 (assertions + installs)

The anchor-removal build actually succeeded (Resolved gcc@16.1.0-musl);
the red came from ci-linux's hardcoded 'Resolved gcc@15.1.0-musl'
assertion. Update every musl 15.1.0 reference across workflows.

Author: Sunrisepeak

.github/workflows/ci-fresh-install.yml

@@ -33,7 +33,7 @@ concurrency:
 
 jobs:
   # ──────────────────────────────────────────────────────────────────
-  # Linux: gcc@16.1.0, musl-gcc@15.1.0, llvm@20.1.7
+  # Linux: gcc@16.1.0, musl-gcc@16.1.0, llvm@20.1.7
   # ──────────────────────────────────────────────────────────────────
   # A4: post-release runs race the xim-pkgindex bump (a PR a maintainer
   # merges asynchronously) — the 0.0.85 fresh-install failed with
@@ -120,16 +120,16 @@ jobs:
 
       - name: "musl-gcc: mcpp new → run"
         run: |
-          mcpp toolchain install gcc 15.1.0-musl
-          mcpp toolchain default gcc@15.1.0-musl
+          mcpp toolchain install gcc 16.1.0-musl
+          mcpp toolchain default gcc@16.1.0-musl
           cd "$(mktemp -d)"
           mcpp new hello_musl
           cd hello_musl
           mcpp run
 
       - name: "musl-gcc: build mcpp"
         run: |
-          mcpp toolchain default gcc@15.1.0-musl
+          mcpp toolchain default gcc@16.1.0-musl
           mcpp clean
           mcpp run
 

.github/workflows/ci-linux-e2e.yml

@@ -115,7 +115,7 @@ jobs:
           # deterministic GNU answer instead of an auto-install pick.
           "$MCPP" toolchain default gcc@16.1.0
           # Warm musl once so fresh-home e2e tests inherit the payload.
-          "$MCPP" toolchain install gcc 15.1.0-musl
+          "$MCPP" toolchain install gcc 16.1.0-musl
           bash tests/e2e/run_all.sh
 
   # ──────────────────────────────────────────────────────────────────

.github/workflows/ci-linux.yml

@@ -121,7 +121,7 @@ jobs:
       # longer relies on e2e's toolchain warm-ups: the GCC build uses the
       # mcpp.toml-pinned default (gcc@16.1.0, already in the sandbox from the
       # self-host build above), and the musl `--target` build auto-installs
-      # gcc@15.1.0-musl on demand (cached across runs).
+      # gcc@16.1.0-musl on demand (cached across runs).
 
       - name: Save freshly-built mcpp for toolchain tests
         run: |
@@ -138,7 +138,7 @@ jobs:
       - name: "Toolchain: musl-gcc — build mcpp (--target)"
         run: |
           "$MCPP" clean
-          "$MCPP" build --target x86_64-linux-musl 2>&1 | tee build.log; grep -q "Resolved gcc@15.1.0-musl" build.log
+          "$MCPP" build --target x86_64-linux-musl 2>&1 | tee build.log; grep -q "Resolved gcc@16.1.0-musl" build.log
 
       - name: "Toolchain: LLVM — build mcpp"
         run: |

mcpp.toml

@@ -22,7 +22,7 @@ macos   = "llvm@22.1.8"
 windows = "llvm@20.1.7"
 
 # Per-target overrides: `mcpp build --target x86_64-linux-musl` (or the
-# four-segment form `x86_64-unknown-linux-musl`) picks musl-gcc 15.1 + full
+# four-segment form `x86_64-unknown-linux-musl`) picks musl-gcc 16.1 + full
 # static linkage. Used by .github/workflows/release.yml to produce a
 # portable static binary that drops in anywhere with no ELF interp / RUNPATH
 # baggage.