docs(bf-qf5mh): document cargo fuzz build command correction

notes/bf-qf5mh.md

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+# Fix for bf-qf5mh: cargo fuzz build command correction
+
+## Problem
+Parent bead bf-4o8a6 had incorrect cargo fuzz build syntax that caused repeated failures:
+- Incorrect: `cargo fuzz build --harness profile_yaml`
+- Correct: `cargo fuzz build profile_yaml`
+
+## Root cause
+cargo-fuzz does not have a `--harness` flag. The target name is passed as a positional argument, not as a flag.
+
+## Verification
+```bash
+$ cargo fuzz build --help
+cargo-fuzz-build 0.13.1
+Build fuzz targets
+
+USAGE:
+    cargo-fuzz build [OPTIONS] [TARGET]
+
+Arguments:
+  [TARGET]
+          Name of the fuzz target to build, or build all targets if not supplied
+```
+
+## Changes made
+Updated bf-4o8a6 description to use correct syntax in both Implementation guidance and Acceptance criteria sections.
+
+## Acceptance criteria status
+- PASS: Documented correct cargo fuzz build syntax (see note)
+- PASS: Parent bead acceptance criteria updated to use `cargo fuzz build profile_yaml`
+- PASS: No reference to --harness flag remains in parent bead