fix(scripts): correct shellcheck source directives that resolved to nothing

`tests/run-tests.sh` declared `source=lib/batch-run.sh`, which resolves
to neither the repo root nor the script's own directory. A directive
that does not resolve is silent: it blinds test-vale-wrap.sh's
`sourced_files()` seeding exemption, and shellcheck's own SC1091 is
`info` while .pre-commit-config.yaml pins `--severity=warning`.

Issue #97 names run-bats.sh's `../scripts/lib/batch-run.sh` as the
correct spelling. It is not. Directives resolve against the source-path,
which under pre-commit is the repo root, so `../scripts/...` escapes the
repo and trips SC1091 exactly as `lib/...` does -- verified directly.
The spelling satisfying both shellcheck and `sourced_files()`'s
two-candidate rule is repo-root-relative, matching scripts/install.sh.

Fixes all three: run-tests.sh, run-bats.sh, and check-manifests.sh,
the last unmentioned by the issue. Every directive in the repo now
resolves, which the previous commit's case 27 asserts.

Refs #97

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01X7GvKuJfy2WrdBmUttV4DT

scripts/check-manifests.sh

@@ -46,7 +46,8 @@ if [[ ! -f "$MARKETPLACE" ]]; then
 fi
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-# shellcheck source=lib/marketplace-plugins.sh
+# Repo-root-relative, not script-dir-relative -- see tests/run-tests.sh for why.
+# shellcheck source=scripts/lib/marketplace-plugins.sh
 source "$SCRIPT_DIR/lib/marketplace-plugins.sh"
 
 # Every local plugin directory marketplace.json claimed, canonicalized, so the