Add a Playwright UI test for the leave-group successor picker

Original task: Add a UI test for the leave-group successor chooser dialog
in artifacts/teaboy-os/src/pages/chat.tsx, mirroring the backend coverage
in artifacts/api-server/tests/conversations-leave.test.mjs.

What I added:
- artifacts/teaboy-os/tests/leave-group-successor.spec.mjs
  A real Playwright e2e test that drives the chat UI in a browser:
  * Cancel path: opens the leave dialog as the sole admin, verifies the
    successor chooser is visible with the auto option pre-selected and
    one option per remaining member, clicks Cancel, and asserts via DB
    that the conversation membership and admin flags are unchanged.
  * Chosen-successor path: re-opens the dialog, picks the *later-joined*
    member (so the choice differs from the auto pick), confirms the
    leave, asserts the POST /conversations/:id/leave call returns 200,
    and verifies via DB that the leaver was removed and the explicitly
    chosen member became the new admin.
  Both tests seed their own users + group via SQL and clean up after
  themselves so they can run repeatedly against the live dev DB.

- artifacts/teaboy-os/playwright.config.mjs
  Minimal Playwright config: testDir=tests, *.spec.mjs match, headless,
  baseURL defaults to http://localhost:80 (the workspace proxy), and
  is overridable via TEST_WEB_BASE.

- artifacts/teaboy-os/package.json
  Added @playwright/test and pg as devDependencies and a `test:e2e`
  script: `playwright test --config playwright.config.mjs`.

- .gitignore
  Ignored Playwright's test-results/ and playwright-report/ output dirs.

How to run:
  pnpm --filter @workspace/teaboy-os exec playwright install chromium
  DATABASE_URL=... pnpm --filter @workspace/teaboy-os run test:e2e

Verification:
  Both tests pass locally (2 passed in ~9s) against the running dev
  workspace. Required system libraries for headless Chromium were
  installed via the workspace's system-deps mechanism (glib, nss, nspr,
  atk, cups, dbus, libdrm, libxkbcommon, libgbm, alsa-lib, pango, cairo,
  and the relevant xorg libs), so `playwright test` works out of the
  box on this environment.

No application source files were modified.

pnpm-lock.yaml

@@ -374,6 +374,9 @@ importers:
       '@hookform/resolvers':
         specifier: ^3.10.0
         version: 3.10.0(react-hook-form@7.71.2(react@19.1.0))
+      '@playwright/test':
+        specifier: ^1.59.1
+        version: 1.59.1
       '@radix-ui/react-accordion':
         specifier: ^1.2.4
         version: 1.2.12(@types/react-dom@19.2.3(@types/react@19.2.14))(@types/react@19.2.14)(react-dom@19.1.0(react@19.1.0))(react@19.1.0)
@@ -518,6 +521,9 @@ importers:
       next-themes:
         specifier: ^0.4.6
         version: 0.4.6(react-dom@19.1.0(react@19.1.0))(react@19.1.0)
+      pg:
+        specifier: ^8.20.0
+        version: 8.20.0
       react:
         specifier: 19.1.0
         version: 19.1.0
@@ -1348,6 +1354,11 @@ packages:
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+  '@playwright/test@1.59.1':
+    resolution: {integrity: sha512-PG6q63nQg5c9rIi4/Z5lR5IVF7yU5MqmKaPOe0HSc0O2cX1fPi96sUQu5j7eo4gKCkB2AnNGoWt7y4/Xx3Kcqg==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   '@radix-ui/number@1.1.1':
     resolution: {integrity: sha512-MkKCwxlXTgz6CFoJx3pCwn07GKp36+aZyu/u2Ln2VrA5DcdyCZkASEDBTd8x5whTQQL5CiYf4prXKLcgQdv29g==}
 
@@ -3180,6 +3191,11 @@ packages:
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     engines: {node: '>=14.14'}
 
+  fsevents@2.3.2:
+    resolution: {integrity: sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==}
+    engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
+    os: [darwin]
+
   fsevents@2.3.3:
     resolution: {integrity: sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==}
     engines: {node: ^8.16.0 || ^10.6.0 || >=11.0.0}
@@ -3808,6 +3824,16 @@ packages:
     resolution: {integrity: sha512-8OEwKp5juEvb/MjpIc4hjqfgCNysrS94RIOMXYvpYCdm/jglrKEiAYmiumbmGhCvs+IcInsphYDFwqrjr7398w==}
     hasBin: true
 
+  playwright-core@1.59.1:
+    resolution: {integrity: sha512-HBV/RJg81z5BiiZ9yPzIiClYV/QMsDCKUyogwH9p3MCP6IYjUFu/MActgYAvK0oWyV9NlwM3GLBjADyWgydVyg==}
+    engines: {node: '>=18'}
+    hasBin: true
+
+  playwright@1.59.1:
+    resolution: {integrity: sha512-C8oWjPR3F81yljW9o5OxcWzfh6avkVwDD2VYdwIGqTkl+OGFISgypqzfu7dOe4QNLL2aqcWBmI3PMtLIK233lw==}
+    engines: {node: '>=18'}
+    hasBin: true
+
   postcss-selector-parser@6.0.10:
     resolution: {integrity: sha512-IQ7TZdoaqbT+LCpShg46jnZVlhWD2w6iQYAcYXfHARZ7X1t/UGhhceQDs5X0cGqKvYlHNOuv7Oa1xmb0oQuA3w==}
     engines: {node: '>=4'}
@@ -5062,6 +5088,10 @@ snapshots:
 
   '@pinojs/redact@0.4.0': {}
 
+  '@playwright/test@1.59.1':
+    dependencies:
+      playwright: 1.59.1
+
   '@radix-ui/number@1.1.1': {}
 
   '@radix-ui/primitive@1.1.3': {}
@@ -6896,6 +6926,9 @@ snapshots:
       jsonfile: 6.2.0
       universalify: 2.0.1
 
+  fsevents@2.3.2:
+    optional: true
+
   fsevents@2.3.3:
     optional: true
 
@@ -7514,6 +7547,14 @@ snapshots:
       sonic-boom: 4.2.1
       thread-stream: 3.1.0
 
+  playwright-core@1.59.1: {}
+
+  playwright@1.59.1:
+    dependencies:
+      playwright-core: 1.59.1
+    optionalDependencies:
+      fsevents: 2.3.2
+
   postcss-selector-parser@6.0.10:
     dependencies:
       cssesc: 3.0.0