Rebase PR #5162 (rename busy_input_mode -> default_message_mode; flip the
default from 'queue' to 'steer') onto current origin/master WITHOUT dropping
the shipped #5170 localStorage persistence mirror.
Rename the mirror machinery to the new setting name for consistency:
_BUSY_INPUT_MODES -> _DEFAULT_MESSAGE_MODES (values unchanged)
_normalizeBusyInputMode -> _normalizeDefaultMessageMode (fallback now 'steer')
_persistBusyInputMode -> _persistDefaultMessageMode
_readPersistedBusyInputMode -> _readPersistedDefaultMessageMode
window._busyInputMode -> window._defaultMessageMode (+ renamed exports)
localStorage: write the new 'hermes-default-message-mode' key; read it with a
fallback to the legacy 'hermes-busy-input-mode' key so an existing user's
persisted preference survives the rename.
Preserve #5170 behavior at every mirror site under the new names:
- boot success -> window._defaultMessageMode=_persistDefaultMessageMode(...)
- boot FAILURE -> window._defaultMessageMode=_readPersistedDefaultMessageMode()
(NOT a hardcoded 'steer' — a saved 'interrupt'/'queue' must still apply when
the server is unreachable; do not regress #5167/#5132)
- preferences autosave, settings-panel load, and _applySavedSettingsUi all
persist through _persistDefaultMessageMode(...)
Tests updated for the rename while keeping the persistence-behavior assertions
(test_1062, test_5145, test_5167); test_5167 gains explicit guards that the
load-failure path reads the persisted pref and never hardcodes a literal mode,
plus autosave/panel-load mirror-write coverage.
Co-authored-by: Rod Boev <rod.boev@gmail.com>
