fix(launcher): resolve release identity for direct task runs (#14)

M3 made MOSAIC_IMAGE_TAG required in compose, but run-task.sh never
called load_release — direct task runs failed in compose before any
model call. release.sh paths masked it by exporting the tag to children.

Found by owner-run test-task.sh; failure receipts were in the run
records' stderr.txt.

Closes #14

scripts/run-task.sh

@@ -11,6 +11,7 @@ cd "$(dirname "$0")/.."
 source scripts/common.sh
 
 load_config
+load_release   # compose requires MOSAIC_IMAGE_TAG; task runs are release-scoped too
 bootstrap_runtime_dir
 
 exec node scripts/mosaic-task.mjs "$@"