Fix three things found by actually using it

**The drag showed no tab.** Moving to pointer events lost the drag image
the OS used to supply, leaving a dimmed source tab and a 2px line —
which reads as "some setting changed", not "I am holding this tab". A
copy of the tab now follows the cursor, carrying its glyph and its real
label, grabbed at the offset it was picked up by so it sits where the
tab was.

**The URL relay opened a different URL than the one on screen.**
Observed: `repo.anhonesthost.net/…/tag/preview-63f3c54` arrived as
`repo.anhonsthost.nt/…/preview-63f3c54Butitprovesyournitpick…`. The
detector deleted *every* line break to undo PTY hard-wrapping, but a
terminal that wraps at a space emits the break **instead of** the space
— so deleting breaks also deletes the separators, gluing the following
paragraph onto the link and running the match past the host.

Only breaks the terminal inserted may be deleted, and those are exactly
the ones at the column width. The detector now takes a live column
getter and rejoins a line only when it is exactly that wide; every other
break becomes a space, which is also what stops a URL match. Lines
*longer* than the width are left alone — the stream had no break there,
so the one that follows is the application's own.

One case stays ambiguous: a URL whose length is an exact multiple of the
width is indistinguishable from one that was cut. That is pinned in a
test as known behaviour rather than papered over — the candidate is
shown in full and nothing opens without the user pressing Open.

**"In container" opened a page nobody could see.** It bound the browser
and stopped, leaving the user to find the Browser tab and press Start,
with nothing saying so — and from a terminal, no pane on screen at all.
Opening a page now starts the viewer if it isn't running, and the
terminal's prompt raises the pop-out window, because that caller has
nowhere else to put it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/components/layout/MainTabs.test.tsx

@@ -127,6 +127,46 @@ describe("MainTabs reordering", () => {
     expect(useAppState.getState().activeTabKey).toBe(HOME);
   });
 
+  it("shows the tab itself under the cursor while dragging", () => {
+    // A dimmed source tab and a thin line do not read as "I am holding this
+    // tab" — the dragged copy is what makes the gesture legible.
+    render(<MainTabs />);
+    const tabs = laidOut();
+    expect(screen.queryByTestId("tab-drag-ghost")).toBeNull();
+
+    pointer(tabs[2], "pointerdown", 250);
+    pointer(tabs[2], "pointermove", 120);
+
+    const ghost = screen.getByTestId("tab-drag-ghost");
+    expect(ghost).toHaveTextContent("shell (bash)");
+    expect(ghost).toHaveTextContent("▣");
+
+    pointer(tabs[2], "pointerup", 120);
+    expect(screen.queryByTestId("tab-drag-ghost")).toBeNull();
+  });
+
+  it("carries the project name when a home tab is dragged", () => {
+    render(<MainTabs />);
+    const tabs = laidOut();
+
+    pointer(tabs[0], "pointerdown", 50);
+    pointer(tabs[0], "pointermove", 250);
+
+    expect(screen.getByTestId("tab-drag-ghost")).toHaveTextContent("api-server");
+    expect(screen.getByTestId("tab-drag-ghost")).toHaveTextContent("⌂");
+  });
+
+  it("drops the dragged copy when the drag is abandoned", () => {
+    render(<MainTabs />);
+    const tabs = laidOut();
+
+    pointer(tabs[2], "pointerdown", 250);
+    pointer(tabs[2], "pointermove", 10);
+    fireEvent.keyDown(window, { key: "Escape" });
+
+    expect(screen.queryByTestId("tab-drag-ghost")).toBeNull();
+  });
+
   it("shows the drop marker only while a drag is under way", () => {
     render(<MainTabs />);
     const tabs = laidOut();