feat(ui): custom modifier editor in-modal docs, recipes, and attr combobox

Surfaces the contents of docs/user/custom-modifiers.md directly inside
the Custom Modifier Editor so authors can compose descriptors without
cross-referencing the guide:

- Per-primitive docs panel in the Parameter Inspector with a longer
  behaviour explanation + one or more worked examples (collapsible).
- Palette hover tooltips now show the full long description plus the
  first example's headline.
- New 'Templates' header button opens a picker with 5 built-in recipes
  (Boosted Pawn, 3-Charge Shield, Aura King, Vampire, Low-HP Fortress).
- AttrCombobox replaces plain text inputs for attr / targetAttr fields.
  Grouped, free-form autocomplete over 17 curated suggestions with a
  'user-defined' badge for out-of-catalog typed names so ShieldCharges-
  style recipes still work.

Primitives gain optional longDescription + examples fields on their
EffectPrimitive descriptor; 15 registrations annotated. Recipe
descriptors pass the existing validator, and new unit tests enforce
doc coverage going forward.

packages/chess/e2e/custom-modifiers.spec.ts

@@ -1322,6 +1322,78 @@ test.describe('T29 — Custom modifier DSL e2e', () => {
       await ctxHost.close();
     }
   });
+
+  test('editor shows docs + examples for selected primitive', async ({
+    page,
+  }) => {
+    await freshLobby(page);
+    await openProfileEditor(page);
+    await openCustomModifierEditor(page);
+
+    // Add a primitive so the inspector renders.
+    await page.getByTestId('custom-primitive-palette-seed-attribute').click();
+    await page.getByTestId('custom-primitive-node-0').click();
+
+    // Docs panel is present with at least one example.
+    const docs = page.getByTestId('custom-primitive-docs');
+    await expect(docs).toBeVisible();
+    await expect(docs).toContainText('seed-attribute');
+    await expect(
+      page.getByTestId('custom-primitive-example-0'),
+    ).toBeVisible();
+  });
+
+  test('AttrCombobox autocompletes known attrs and accepts user-defined names', async ({
+    page,
+  }) => {
+    await freshLobby(page);
+    await openProfileEditor(page);
+    await openCustomModifierEditor(page);
+
+    // Add a seed-attribute primitive so the attr field renders.
+    await page.getByTestId('custom-primitive-palette-seed-attribute').click();
+    await page.getByTestId('custom-primitive-node-0').click();
+
+    const combobox = page.getByTestId('primitive-seed-attribute-attr');
+    await expect(combobox).toBeVisible();
+
+    // Focus the input; the dropdown should open with groups visible.
+    const input = page.getByTestId('primitive-seed-attribute-attr-input');
+    await input.click();
+    await expect(
+      page.getByTestId('primitive-seed-attribute-attr-dropdown'),
+    ).toBeVisible();
+
+    // Click the "Hp" suggestion — input value updates and dropdown closes.
+    await page.getByTestId('attr-combobox-option-Hp').first().click();
+    await expect(input).toHaveValue('Hp');
+
+    // Type a user-defined attr name — badge appears, dropdown filters down.
+    await input.fill('MyStacks');
+    await expect(combobox).toContainText('user-defined');
+  });
+
+  test('Templates picker loads a recipe into the editor', async ({ page }) => {
+    await freshLobby(page);
+    await openProfileEditor(page);
+    await openCustomModifierEditor(page);
+
+    // Open the templates modal and pick the shield recipe (2 primitives).
+    await page.getByTestId('custom-templates').click();
+    await expect(page.getByTestId('custom-templates-modal')).toBeVisible();
+    await page
+      .getByTestId('custom-template-recipe-three-charge-shield')
+      .click();
+
+    // Modal closes and the tree is populated with the recipe's primitives.
+    await expect(page.getByTestId('custom-templates-modal')).toHaveCount(0);
+    await expect(page.getByTestId('custom-primitive-node-0')).toBeVisible();
+    await expect(page.getByTestId('custom-primitive-node-1')).toBeVisible();
+    // Name field reflects the template's descriptor.name.
+    await expect(
+      page.locator('input[placeholder="Modifier Name"]'),
+    ).toHaveValue('3-Charge Shield');
+  });
 });
 
 // ─── WS helpers (mirrored from modifier-profiles.spec.ts) ──────────