Fix HIGH and MEDIUM frontend defects

Files pane
- F16: a drag-out released back inside the app no longer re-imports its own
  staged copy over the container original. An in-flight flag (cleared from the
  drag plugin's `onEvent` channel, with a watchdog) suppresses the drop and the
  "Drop files into …" hint, and an exact staged-path filter is the second line
  of defence — the `path|size|modified` cache could otherwise write a
  minutes-old snapshot over a file an agent had since rewritten.
- F17: a slow upload/rename no longer yanks the user back to the directory the
  operation started in. Every operation captures its target path and re-lists
  only if the user is still there; failures go to the toast host either way.
- The grid keeps keyboard focus. Roving tabindex (one tab stop, not one per
  row) plus focus restore after navigation, rename commit/cancel and Escape.
- Transient failures now surface in `ToastHost` (z-[60], persistent aria-live)
  instead of a `role="alert"` 300 rows down a scroller or behind a modal
  overlay. The inline error is kept only for the listing failure.
- `navigate` is sequenced by generation; "Save to host…" sets `busy`.
- Grid a11y: column headers, a text affordance for folder vs file, a live
  region that is mounted empty and announces completion, Label-in-Name fixed.
- FileViewerModal: the blob URL is released only once its replacement exists;
  the preview is a focusable, named, scrollable region.

Native drop routing
- New `lib/dropTarget.ts`: the hit test now refuses a drop while any
  `[aria-modal="true"]` dialog or `[data-blocks-drop]` overlay is up, and
  checks z-order where the environment can answer it. Shared by FilesTab and
  TerminalView; App's shutdown overlay opts in.

Disk
- A partially failed reclaim says so in words ("… — 2 of 5 failed"), not by hue
  alone.
- The scan/reclaim race is closed: every mutation retires an in-flight scan, so
  a scan can no longer repaint a pre-reclaim report plus a clickable plan of
  objects that are gone. Scan is disabled while working; the status is a live
  region; a failed destructive action keeps its dialog open and reports there.
- The "unknown" layer count gets a screen-reader fallback; `--text-disabled`
  no longer carries live information.

Terminal / OAuth
- After the toast is dismissed, a truncated heuristic guess can no longer fill
  the slot that an exact OSC 8 or relay URL occupied — the detector remembers
  every exact URL and drops any candidate that is a strict prefix of one.
- The prompt is reachable by keyboard: Ctrl+Shift+O jumps to the default
  action, Escape dismisses, focus returns to the terminal, and auto-dismiss
  holds off while focus is inside. It deliberately does not steal focus.
- UrlToast renders through `ui/Button` and `--shadow-overlay`.

Elsewhere
- AuthBridgeRow: a pushed `auth-bridge-changed` status always outranks an older
  awaited toggle result.
- The last two ad-hoc byte formatters route through `lib/formatBytes`.

Contract for the backend agent: `upload_file_to_container` refusing to
overwrite must satisfy `isFileExistsError` in `src/lib/uploadErrors.ts` (marker
`FILE_EXISTS`) and accept an `overwrite` argument; the frontend turns that into
an `ui/Modal` Replace/Skip prompt rather than a raw error string.

Tests: 536 -> 627 passing. `npm run build` and `npx tsc --noEmit` green.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBq2rGum6GX7xXgsas1fDc

app/src/components/projects/home/config/RuntimeSection.test.tsx

@@ -107,6 +107,58 @@ describe("RuntimeSection — VPN support toggle", () => {
   });
 });
 
+/**
+ * `scope="project"` on the settings editor is one prop with no visible owner,
+ * and deleting it fails silently in the worst possible direction: the editor
+ * falls back to `"global"`, every three-state control collapses to an on/off
+ * switch, and a field the project is *inheriting* as on renders flat Off. The
+ * user then reads a lie and, worse, flipping that switch writes a deliberate
+ * `false` that overrides the global On they thought they were looking at.
+ *
+ * Nothing asserted the prop was passed, so these go through what is rendered
+ * rather than through props — a switch where a select belongs is exactly the
+ * regression, and it is visible from the outside.
+ */
+describe("RuntimeSection — Claude Code settings are edited at project scope", () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it("gives every setting the third Global state a project can inherit through", () => {
+    renderSection();
+    const focus = screen.getByLabelText("Focus mode") as HTMLSelectElement;
+    expect(
+      Array.from(focus.querySelectorAll("option")).map((o) => o.getAttribute("value")),
+    ).toEqual(["global", "off", "on"]);
+  });
+
+  it("renders an untouched setting as inheriting, not as Off", () => {
+    // `claude_code_settings: null` means "this project has no opinion", which
+    // is not the same instruction as off. At global scope the same field is a
+    // plain unchecked switch — indistinguishable from a user who turned it
+    // off, and the reason the missing prop would never be noticed.
+    renderSection({ claude_code_settings: null });
+    expect((screen.getByLabelText("Focus mode") as HTMLSelectElement).value).toBe(
+      "global",
+    );
+    expect(screen.queryByRole("switch", { name: "Focus mode" })).not.toBeInTheDocument();
+  });
+
+  it("keeps a stored project override visible over the inherited value", () => {
+    renderSection({
+      claude_code_settings: {
+        tui_mode: null,
+        effort: null,
+        auto_scroll_disabled: null,
+        focus_mode: true,
+        show_thinking_summaries: null,
+        session_recap_disabled: null,
+        env_scrub: null,
+        prompt_caching_1h: null,
+      },
+    });
+    expect((screen.getByLabelText("Focus mode") as HTMLSelectElement).value).toBe("on");
+  });
+});
+
 describe("RuntimeSection — auth bridge toggle", () => {
   beforeEach(() => vi.clearAllMocks());