feat(feed): bound feed lifecycle to 30-day window with nonblocking refresh

Persisted feeds keep only episodes from the last 30 days (plus completed
downloads); older episodes live in volatile memory and survive refreshes
via union merge, with per-feed in-memory caches capped at 500. Refresh
batches run at FETCH_CONCURRENCY=4 with per-feed incremental apply (no
Promise.all barrier), config.json writes are trailing-edge debounced
(250ms, immediate flushPendingSave for unsubscribes), and cold
fetch-more refetches abort at FETCH_TIMEOUT_MS. A shared activity store
powers a global top-right indicator covering refresh, fetch-more,
subscribe, search, and downloads.

Also includes the in-flight incremental RSS parsing (chunked with
event-loop yields) and refresh spinner work this tree already carried.

tests/yazi-pane-row.test.tsx

@@ -66,6 +66,7 @@ type TestPaneProps = {
 	current?: (() => unknown) | unknown;
 	preview?: unknown;
 	focused?: unknown;
+	currentBorder?: unknown;
 	width?: number;
 	height?: number;
 };
@@ -83,6 +84,7 @@ async function renderPaneRow(props: TestPaneProps): Promise<{
 					preview={props.preview as any}
 					currentLabel="List"
 					focused={props.focused as any}
+					currentBorder={props.currentBorder as any}
 				/>
 			</ThemeProvider>
 		),
@@ -232,4 +234,17 @@ describe("PaneRow current-pane borders", () => {
 		expect(borderColumns(spans)).toEqual([20, 69]);
 		expect(frameText(spans)).not.toMatch(boxGlyphs);
 	});
+
+	test("currentBorder=['left'] removes the right edge (left only)", async () => {
+		const { spans, destroy } = await renderPaneRow({
+			parent: null,
+			current: () => <text>ITEM</text>,
+			preview: null,
+			currentBorder: ["left"],
+		});
+		cleanups.push(destroy);
+		// Only the left border glyph at column 20 — no right edge at 69.
+		expect(borderColumns(spans)).toEqual([20]);
+		expect(frameText(spans)).not.toMatch(boxGlyphs);
+	});
 });