framework tools/git: strict value guards + provider-failure normalization family-wide (codex blockers on PR #1464)

- Value guards now reject option-like values: --anything always, and
  single-dash flag shapes (-h, -i). Previously -b --help consumed
  --help as the body and performed the write (codex example:
  issue-close -i --help proceeding to 'Closed GitHub issue #--help').
  Multi-char dash-leading text (-start of a list) stays a legal value.
- Every remaining direct provider exec (gh/tea/CMD arrays across
  issue-create/edit/assign/list/view, milestone-*, pr-create/edit,
  pr-close, issue-close/reopen) wrapped with rc capture and normalized
  to exit 1 with a stderr message — provider exit 2 no longer collides
  with the reserved usage-error status.
- All 16 usage-contract suites gained option-like and short-flag arms
  (16/16 green). Existing suites re-verified; test-pr-edit and
  test-issue-create-interactive-auth fail identically with these
  changes stashed (environment-coupled, not regressions; documented).

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

@@ -21,7 +21,7 @@ STATE="open"
 while [[ $# -gt 0 ]]; do
     case $1 in
         -s|--state)
-            [[ $# -ge 2 ]] || usage_error "option $1 requires a value"
+            [[ $# -ge 2 && "$2" != --* && ! "$2" =~ ^-[a-zA-Z]$ ]] || usage_error "option $1 requires a value (option-like values are rejected)"
             STATE="$2"
             shift 2
             ;;
@@ -42,13 +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