Fix the dead win7 context menu, flatten the selection, add a tab menu

Right-click did nothing under the win7 skin, and then swallowed the next
click. 7.css declares `position: relative` on ul[role=menu] and the `skin`
layer outranks `utilities`, so Tailwind's `.fixed` lost: [style.left/top.px]
became flow offsets from the menu's static position — the last child of the
h-screen frame — and every menu rendered below the viewport, unreachable
behind overflow:hidden. Its backdrop is a plain <div>, unmatched by 7.css, so
that stayed genuinely fixed and ate the following click. Regressed in 0ae2a62,
when the menu adopted 7.css's real markup.

Restated `position: fixed` in skinfix, scoped to a new `w7-ctx` marker so
7.css's own menus keep theirs. scripts/menu-probe.ts is the regression test:
it renders the menu at declared coordinates, pixel-scans whether it landed
there, and carries a marker-less control menu (the bug verbatim) as its own
discriminator. A resting pixel diff cannot see this class of bug.

Selection band goes flat: --w7-sel-bg/-bd (#cbe8f6/#26a0da) is what Explorer
actually painted, where 7.css reused --w7-el-grad-h, its Aero element-hover
ramp. That var is left alone — buttons and tabs still want the gloss. The
unfocused pane gets the grey idle band; the band still never disappears with
focus, it only weakens. Harness diff confirms the change touches selection
rows and nothing else, in both themes.

New workspace-tab right-click menu in both skins: New Tab, Close Tab, Close
Other Tabs, Close Tabs to the Right, Disconnect. The target id travels inside
the action string because the right-clicked tab is not necessarily the active
one. Illegal entries are disabled rather than omitted, the way Win7 greyed
out — and since 7.css's [aria-disabled] handling is CSS-only, the keyboard
paths check the flag themselves.

Co-Authored-By: Claude <noreply@anthropic.com>

src/shared/i18n/ja.ts

@@ -294,6 +294,11 @@ export const ja = {
 		copyPath: "パスをコピー",
 		delete: "削除",
 		columns: "列",
+		tabNew: "新しいタブ",
+		tabClose: "タブを閉じる",
+		tabCloseOthers: "他のタブを閉じる",
+		tabCloseRight: "右側のタブを閉じる",
+		tabDisconnect: "切断",
 		trashTooltip: "ここからゴミ箱に入れた項目は Finder の「戻す」を利用できません",
 	},
 	errors: {