fix(studio): chip away explicit-tabindex ratchet debt (#48040)

## What kind of change does this PR introduce?

A11y cleanup follow-up to #47984 /
[DEPR-626](https://linear.app/supabase/issue/DEPR-626).

## What is the current behavior?

Studio had 82 ratcheted `supabase/require-explicit-tabindex` violations
(raw `<button>` / `role="button"` without explicit `tabIndex`).

## What is the new behavior?

- Explicit `tabIndex={0}` (or disabled → `-1`) on those Studio call
sites across nav, `components/ui`, Database, Storage, and the remainder
- Ratchet baseline cleared (**82 → 0**) and the rule **removed from the
Studio ratchet** (debt is gone; ratchet is temporary)
- Rule remains a shared **`warn`** for now — promoting to `error` (and
sweeping www/docs/design-system) is a follow-up
- Also fixed the learn/ui-library call sites that surfaced while
experimenting with error promotion
- Small follow-ups where making controls focusable exposed gaps:
accessible names, disabled/focus consistency, focus-ring polish on
To-test surfaces, home section `KeyboardSensor`, and an E2E locator
tightened after `aria-label="Remove column"`

Prefer migrating to `Button` from `ui` in future touch-ups; this PR
takes the minimal path so Studio debt can stay at zero.

## Additional context

Batches landed together so baseline conflicts stayed simple while
chipping away:

- Hotspots / nav (FirstLevelNav, Marketplace, AttachmentUpload, Column,
Tabs, …)
- `components/ui` shared
- Database + Storage
- Remainder

**Out of scope / intentional deferrals**

- Promoting `supabase/require-explicit-tabindex` to a lint **error**
(follow-up after www/docs/design-system sweeps)
- Tabs/Radio roving, tooltips, context menus, in-menu items
- Full keyboard-accessible tab-close UX (close stays hover +
`tabIndex={-1}`; context menu still closes tabs)
- Data API docs links (`/project/<ref>/api` redirect)

**Reviewer notes**

- Rule only flags raw `<button>` / `role="button"` without a `tabIndex`
prop. `Button` from `ui` already bakes this in
- `tabIndex={-1}` is intentional for disabled controls, in-menu /
roving-focus children, and hover-only tab close
- For dnd-kit grips, put `tabIndex` **after** `{...attributes}` so it
isn’t overwritten (TS2783)

### To test

Use **Safari** with macOS Keyboard navigation **off** (System Settings →
Keyboard). Chrome once for a sanity pass. For each surface below: Tab
until the control is focused, then activate with Enter/Space where
relevant.

1. **API Docs side panel** (Table Editor → open a table → **API docs**)
- Floating API Docs panel — **not** `/project/<ref>/api` (that redirects
to Data API docs; language ToggleGroup uses arrow keys; links are out of
scope)
- Left nav buttons — Tab through several and activate one; active
highlight / navigation still works

2. **Integrations → Marketplace**
- Enable **Integrations layout** feature preview first (avatar menu →
Feature previews)
   - `/org/<slug>/integrations` or project integrations marketplace
   - “Clear all”, grid/list toggles — Tab + activate

3. **Table Editor → create a table → Columns**
- Drag handles only appear while **creating** (not when editing an
existing table)
   - Tab to grip / remove (X) / sensitive-data eye if shown

4. **Project Home** — section drag handles
   - Tab to a grip (visible focus ring)
- Optional: Space to pick up, arrows to move, Space/Esc to drop
(KeyboardSensor added)
   - Mouse dnd still works

5. **Storage → Policies** — expand/collapse bucket list chevron
(design-system focus ring, no stuck grey open bg)

6. **Support form** (Help → Support) — attachment remove (×) and
add-attachment control when visible

Disabled controls should be **skipped** by Tab.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Accessibility Improvements**
* Improved keyboard navigation throughout Studio by explicitly managing
focus (`tabIndex`) across many interactive controls (menus, tabs,
tables, charts, dialogs, navigation, and form actions).
* Disabled or non-interactive controls are now removed from the tab
order (or made unfocusable), while available actions remain reachable.
* Ensured `type="button"` on relevant controls to prevent unintended
submissions, and refined keyboard focus behavior for various toggles and
copy/remove actions.
* **Chores**
* Updated the ESLint rule baseline configuration to match the new focus
behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

e2e/studio/features/table-editor.spec.ts

@@ -1,5 +1,7 @@
 import fs from 'fs'
 import path from 'path'
+import { expect, Page } from '@playwright/test'
+
 import { env } from '../env.config.js'
 import { expectClipboardValue } from '../utils/clipboard.js'
 import { dropTable, query } from '../utils/db/index.js'
@@ -14,7 +16,6 @@ import {
   waitForGridDataToLoad,
   waitForTableToLoad,
 } from '../utils/wait-for-response.js'
-import { expect, Page } from '@playwright/test'
 
 const deleteTable = async (page: Page, ref: string, tableName: string) => {
   const viewLocator = page.getByLabel(`View ${tableName}`)
@@ -1254,7 +1255,7 @@ testRunner('table editor', () => {
     await expect(page.getByRole('link', { name: 'public.pw_table_fk_target' })).toBeVisible()
 
     // Remove the foreign key relation
-    await page.getByRole('button', { name: 'Remove' }).click()
+    await page.getByRole('button', { name: 'Remove', exact: true }).click()
 
     // Save the table changes after removing foreign key
     const removeFkPromise = waitForApiResponseWithTimeout(