/* メールのフォルダツリー（Thunderbird と同じ階層）— js/workspace/mail-tree.js。Mac（index.html）と iPhone（mobile.html）で共用 */
.mt-sec { margin: 12px 0; } .mt-sec h4, .mt-h { margin: 14px 0 6px; font-size: 13px; letter-spacing: .02em; opacity: .9; }
.mt-dry { color: #ffd27a; }
.mt-tree { display: flex; flex-direction: column; gap: 4px; }
.mt-a { border: 1px solid rgba(140,170,210,.22); border-radius: 8px; padding: 2px 0; }
.mt-acc, .mt-f, .mt-tw { all: unset; box-sizing: border-box; cursor: pointer; }
.mt-acc { display: flex; align-items: center; gap: 6px; width: 100%; padding: 8px 10px; font-weight: 600; }
.mt-row { display: flex; align-items: center; min-height: 32px; border-radius: 6px; }
.mt-row.on { background: rgba(80,160,255,.18); }
.mt-tw { display: inline-flex; justify-content: center; width: 1.6em; min-height: 28px; align-items: center; opacity: .75; flex: none; }
.mt-f { flex: 1; padding: 5px 8px 5px 2px; white-space: pre; overflow: hidden; text-overflow: ellipsis; }   /* pre: 末尾の空白（「K&S 」）も見える */
.mt-acc:focus-visible, .mt-f:focus-visible, .mt-tw:focus-visible { outline: 2px solid rgba(120,200,255,.7); outline-offset: -2px; }
.mt-n { display: inline-block; min-width: 1.5em; padding: 0 6px; border-radius: 9px; font-size: 11px; line-height: 17px; text-align: center;
        background: rgba(80,160,255,.28); color: #cfe8ff; font-weight: 600; margin-left: 4px; }
@media (hover: hover) { .mt-acc:hover, .mt-f:hover { color: #bfe3ff; } }