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/pr-close.sh

@@ -24,14 +24,14 @@ usage_error() {
 while [[ $# -gt 0 ]]; do
     case $1 in
         -n|--number)
-            [[ $# -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)"
             PR_NUMBER="$2"
             shift 2
             ;;
         -b|--body|-c|--comment)
             # R1 (2026-08-28): --body is the canonical flag; -c/--comment stays
             # a backward-compatible alias.
-            [[ $# -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)"
             COMMENT="$2"
             shift 2
             ;;
@@ -79,9 +79,13 @@ if [[ "$PLATFORM" == "github" ]]; then
     echo "Closed GitHub PR #$PR_NUMBER"
 elif [[ "$PLATFORM" == "gitea" ]]; then
     if [[ -n "$COMMENT" ]]; then
-        tea pr comment "$PR_NUMBER" "$COMMENT" $(get_gitea_repo_args)
+        prov_rc=0
+        tea pr comment "$PR_NUMBER" "$COMMENT" $(get_gitea_repo_args) || prov_rc=$?
+        [[ "$prov_rc" -eq 0 ]] || { echo "Error: provider command failed (exit ${prov_rc}; provider failure, not a usage error)" >&2; exit 1; }
     fi
-    tea pr close "$PR_NUMBER" $(get_gitea_repo_args)
+    prov_rc=0
+    tea pr close "$PR_NUMBER" $(get_gitea_repo_args) || prov_rc=$?
+    [[ "$prov_rc" -eq 0 ]] || { echo "Error: provider command failed (exit ${prov_rc}; provider failure, not a usage error)" >&2; exit 1; }
     echo "Closed Gitea PR #$PR_NUMBER"
 else
     echo "Error: Unknown platform"