Buffer and conditionally drop a pending GOP when an upstream loop/restart emits a premature IDR. mp4.go: add gopBuffer and bufferedSample types, hold samples until the next video keyframe, detect a seam by comparing the new keyframe interval against the previous cadence (SeamGapDivisor) and drop the short/truncated tail GOP or commit buffered samples. Add commitBufferedGOP and commitSampleToTrack helpers and flush the final buffered GOP on Close. mp4_loopseam_test.go: update test descriptions, expectations and names to assert the truncated tail GOP is dropped exactly once across different GOP sizes. Dockerfile and Dockerfile.arm64: re-declare ARG VERSION inside the build stage and only derive git describe when VERSION is unset or the default 0.0.0 so build-arg values are respected. Add a binary MP4 fixture used by the tests.
Pass VERSION from CI into Docker builds and embed it into the Go binary via ldflags. Updated .github workflow to supply --build-arg VERSION for both architectures. Added ARG VERSION and logic in Dockerfile and Dockerfile.arm64 to derive the version from git (git describe --tags) or fall back to the provided build-arg, then set it with -X during go build. Changed VERSION in machinery/src/utils/main.go from a const to a var defaulting to "0.0.0" and documented that it is overridden at build time. This ensures released images contain the correct agent version while local/dev builds keep a sensible default.
