build(justfile): anchor the fuzz recipe to one exact target

Assisted-by: GLM 5.3

justfile

@@ -77,8 +77,10 @@ unit pkgs=packages run=".*":
     systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test -timeout 0 {{pkgs}} -run '{{run}}'
 
 # Time-boxed fuzz of one target in one package. The package is required; never a gate.
+# The target is anchored so an exact name matches one target: `FuzzParse` would
+# otherwise select `FuzzParseExpand` beside it.
 fuzz target pkg fuzztime="60s":
-    systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test -timeout 0 -run '^$' -fuzz '{{target}}' -fuzztime={{fuzztime}} -parallel={{fuzzparallel}} {{pkg}}
+    systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test -timeout 0 -run '^$' -fuzz '^{{target}}$' -fuzztime={{fuzztime}} -parallel={{fuzzparallel}} {{pkg}}
 
 # The cmd/link GOOBJ parity gate, opt-in: it costs minutes no pipeline can afford.
 link-parity: