Pure-shell perf work focused on the keystroke→event→redraw path,
validated across bash/zsh/ksh93/mksh/busybox with byte-identical behavior.

- ord.sh: make _tuish_ord fork-free for bytes >=128. The old non-ASCII
  fallback forked $(printf '%d' ...) once per UTF-8 byte. Now bash/zsh use
  a fork-free `printf -v` path and other shells a generated case keyed on
  the chr table (extended to 255). Returns unsigned 1-255, which also makes
  event.sh's UTF-8 lead-byte checks reliable on signed-char platforms.
- hid.sh: collapse up to 24 sequential modifier-helper calls per modified
  key into one head-case + one modifier-case (modifier slot anchored as
  exactly two digits, rejecting extra-parameter sequences). Resolve the
  most frequent class C (typing) first via early return. Remove the now
  unused _tuish_5code/6code_modifiers helpers.
- str.sh: inline the UTF-8 decode in tuish_str_width over the local value,
  dropping the per-byte eval indirection; codepoint arithmetic unchanged.

Adds a headless cross-shell benchmark harness under tests/bench/ and a
resolver-level golden test (tests/unit/test_event_modifiers.sh) covering the
full key x modifier cross product; folds the direct-helper tests into it.