p0 line landing: coord board/roll + wrapper usage contract + dispatch layer (successor to #1467) (#1468)

Co-authored-by: orch-01 <[email protected]>

packages/mosaic/framework/tools/git/milestone-list.sh

@@ -8,11 +8,20 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 source "$SCRIPT_DIR/detect-platform.sh"
 
 # Parse arguments
+# Usage-error contract (R4, 2026-08-28): usage errors print to STDERR and exit 2,
+# distinct from provider, credential, and verification failures (exit 1).
+usage_error() {
+    echo "Error: $*" >&2
+    echo "Usage: milestone-list.sh [-s <state>] (see --help)" >&2
+    exit 2
+}
+
 STATE="open"
 
 while [[ $# -gt 0 ]]; do
     case $1 in
         -s|--state)
+            [[ $# -ge 2 && "$2" != - && "$2" != --* && ! "$2" =~ ^-[[:alnum:]] ]] || usage_error "option $1 requires a value (option-like values are rejected; bare - is reserved)"
             STATE="$2"
             shift 2
             ;;
@@ -25,8 +34,7 @@ while [[ $# -gt 0 ]]; do
             exit 0
             ;;
         *)
-            echo "Unknown option: $1"
-            exit 1
+            usage_error "unknown option: $1"
             ;;
     esac
 done
@@ -34,13 +42,17 @@ done
 detect_platform >/dev/null
 
 if [[ "$PLATFORM" == "github" ]]; then
-    gh api "/repos/{owner}/{repo}/milestones?state=$STATE" --jq '.[] | "\(.title) (\(.state)) - \(.open_issues) open, \(.closed_issues) closed"'
+    prov_rc=0
+    gh api "/repos/{owner}/{repo}/milestones?state=$STATE" --jq '.[] | "\(.title) (\(.state)) - \(.open_issues) open, \(.closed_issues) closed"' || prov_rc=$?
+    [[ "$prov_rc" -eq 0 ]] || { echo "Error: provider command failed (exit ${prov_rc}; provider failure, not a usage error)" >&2; exit 1; }
 elif [[ "$PLATFORM" == "gitea" ]]; then
     REPO_ARGS=$(get_gitea_repo_args) || {
         echo "Error: Could not resolve Gitea repo/login for remote host" >&2
         exit 1
     }
-    tea milestone list $REPO_ARGS
+    prov_rc=0
+    tea milestone list $REPO_ARGS || prov_rc=$?
+    [[ "$prov_rc" -eq 0 ]] || { echo "Error: provider command failed (exit ${prov_rc}; provider failure, not a usage error)" >&2; exit 1; }
 else
     echo "Error: Unknown platform"
     exit 1