v0.1.16

Skip unchanged nightlies

• New nightly-guard composite action (.github/actions/nightly-guard). A scheduled nightly skips its expensive lane only when the latest successful scheduled run already covers the current default-branch SHA and finished less than seven days ago.
• Manual workflow_dispatch runs always run, and the seven-day floor keeps drift coverage for dependencies and external services.
• The guard fails open: any API error, parse failure or ambiguity runs the nightly. An intentional skip counts as healthy in qualification.
• tool-nightly.yml runs the guard on ubuntu-slim and needs actions: read. Callers must grant permissions: actions: read.