framework tools/git: guards reject all option-shaped values; usage_error routes usage to stderr (codex round on PR #1464)

- Option-like value = any token starting with '-' followed by an
  alphanumeric (-h, -ab, --help); multi-character short clusters were
  still accepted (codex blocker). Bare '-' is reserved (future stdin).
- usage_error now prints the usage text to stderr as well (codex
  should-fix): usage output belonged to stdout only on the help path.
- 16/16 usage-contract suites green.

packages/mosaic/framework/tools/git/issue-view.sh

@@ -82,7 +82,7 @@ if comments:
 while [[ $# -gt 0 ]]; do
     case $1 in
         -i|--issue)
-            [[ $# -ge 2 && "$2" != --* && ! "$2" =~ ^-[a-zA-Z]$ ]] || usage_error "option $1 requires a value (option-like values are rejected)"
+            [[ $# -ge 2 && "$2" != - && "$2" != --* && ! "$2" =~ ^-[[:alnum:]] ]] || usage_error "option $1 requires a value (option-like values are rejected; bare - is reserved)"
             ISSUE_NUMBER="$2"
             shift 2
             ;;