Fix new secret form textarea overflow (PAPA-348) (#6222)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Operators manage per-company secrets through the Secrets page in the
web UI
> - A long secret value pasted into the "New secret" textarea blew out
the form's width, which pushed the Create/Cancel buttons off-screen and
made the form unusable
> - Root cause: the shadcn `Textarea` primitive sets `w-full` but does
not constrain `min-width`, so a flex parent honors the textarea's
intrinsic content width when a long unbreakable string is present
> - This pull request adds `min-w-0 max-w-full` to the shared `Textarea`
primitive and `min-w-0 overflow-x-hidden break-all` on the secret-value
usage so a long token wraps inside the form bounds
> - The benefit is the Create/Cancel buttons stay reachable regardless
of pasted token length, and every other `Textarea` consumer also gets
the flexbox-friendly width constraint

## What Changed

- `ui/src/components/ui/textarea.tsx`: added `min-w-0 max-w-full` to the
base shadcn `Textarea` so it cannot exceed its flex parent
- `ui/src/pages/Secrets.tsx`: added `min-w-0 overflow-x-hidden
break-all` on the new-secret value `Textarea` so long opaque tokens wrap
instead of pushing the form
- `ui/src/pages/Secrets.render.test.tsx`: new regression test that opens
the New Secret dialog and asserts the value textarea carries the
width-constraint classes

## Verification

- `cd ui && npx vitest run src/pages/Secrets.render.test.tsx` — 3/3 pass
- Manual: open the Secrets page, click "New secret", paste a long
unbroken string (e.g. a 500-char token) into the value field. The form
stays within its dialog and the Create/Cancel buttons remain in view.

Before:

<img width="1772" height="1432" alt="image"
src="https://github.com/user-attachments/assets/cb31a290-f82a-41dc-9346-91d18cbb5911"
/>

After:

<img width="672" height="734" alt="Screenshot 2026-05-17 at 5 39 38 PM"
src="https://github.com/user-attachments/assets/a08800c2-b09b-43be-b0e8-114d9149b8f5"
/>

After: the value field wraps with `break-all` inside the dialog;
Create/Cancel stay clickable. Covered by the new render test which
asserts `min-w-0`, `overflow-x-hidden`, and `break-all` are present on
`#new-secret-value`.

## Risks

- Low risk. The base `Textarea` change adds `min-w-0 max-w-full`, which
only affects layouts where a textarea was previously allowed to grow
past its parent — those cases were already buggy. `break-all` on the
secret-value textarea is the right behavior for opaque tokens; it would
be wrong for prose, but this field is explicitly a secret token.

## Model Used

- Provider: Anthropic Claude
- Model: claude-opus-4-7 (Opus 4.7)
- Mode: standard Claude Code agent, tool use enabled

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] If this change affects the UI, I have included before/after
screenshots
- [ ] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

ui/src/components/ui/textarea.tsx

@@ -7,7 +7,7 @@ function Textarea({ className, ...props }: React.ComponentProps<"textarea">) {
     <textarea
       data-slot="textarea"
       className={cn(
-        "border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
+        "border-input placeholder:text-muted-foreground focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive dark:bg-input/30 flex field-sizing-content min-h-16 min-w-0 w-full max-w-full rounded-md border bg-transparent px-3 py-2 text-base shadow-xs transition-[color,box-shadow] outline-none focus-visible:ring-[3px] disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
         className
       )}
       {...props}

ui/src/pages/Secrets.render.test.tsx

@@ -305,4 +305,43 @@ describe("Secrets page layout", () => {
       root.unmount();
     });
   });
+
+  it("keeps the new secret value textarea width-constrained for long tokens", async () => {
+    const root = createRoot(container);
+    const queryClient = new QueryClient({
+      defaultOptions: { queries: { retry: false } },
+    });
+
+    await act(async () => {
+      root.render(
+        <MemoryRouter>
+          <QueryClientProvider client={queryClient}>
+            <Secrets />
+          </QueryClientProvider>
+        </MemoryRouter>,
+      );
+    });
+    await flushReact();
+    await flushReact();
+
+    const newSecretButton = Array.from(container.querySelectorAll("button")).find(
+      (button) => button.textContent?.includes("New secret"),
+    ) as HTMLButtonElement | undefined;
+    expect(newSecretButton).toBeDefined();
+
+    await act(async () => {
+      newSecretButton?.click();
+    });
+    await flushReact();
+
+    const secretValueTextarea = document.body.querySelector("#new-secret-value") as HTMLTextAreaElement | null;
+    expect(secretValueTextarea).not.toBeNull();
+    expect(secretValueTextarea?.className).toContain("min-w-0");
+    expect(secretValueTextarea?.className).toContain("overflow-x-hidden");
+    expect(secretValueTextarea?.className).toContain("break-all");
+
+    await act(async () => {
+      root.unmount();
+    });
+  });
 });

ui/src/pages/Secrets.tsx

@@ -1224,7 +1224,7 @@ export function Secrets() {
                       setCreateForm((current) => ({ ...current, value: event.target.value }))
                     }
                     rows={3}
-                    className="font-mono text-xs"
+                    className="min-w-0 overflow-x-hidden break-all font-mono text-xs"
                     placeholder="Stored once, never re-displayed"
                   />
                 </div>