app-version route stale self-description — documents a stale-bundle-guard client that doesn't exist

src/app/api/app-version/route.ts documents itself as serving 'the proactive stale-bundle guard (bwi#293)' where a client compares baked-in version to live. That client has zero callers anywhere in src/ outside two test assertions. The real skew guard (PLUTO-171 route-manifest.ts) is server-side 404 classification, not a client fetch. Route is force-dynamic+no-store for a consumer that was never wired or was removed. Same shape as the context-warn doc-hazard (v2.22.41): comment describing a live mechanism that isn't there. Found by coder-pluto-cc 2026-07-31 while measuring the context-warn fix, not fixed/pushed. Fix: correct the comment to describe reality (route still serves live PTD version-match probes; drop the bwi#293/stale-bundle-guard framing) or remove the dead-client framing entirely. Not urgent — fold into next neighborhood touch, no standalone deploy required.