fix: keep password form visible on validation error

The password setup/change form used hx-target="#password-section" with
hx-swap="innerHTML", but that div wraps the form itself. On a validation
error the route returns only an alert div, so the swap replaced the entire
form — the password inputs disappeared. Most visible during registration's
"set password" step.

Retarget the form to a dedicated #password-error div outside the form
(mirrors the working login form's #login-error pattern), so the form and
its inputs survive errors while messages still render inside #password-section.

Also fix pre-existing broken e2e tests: they omitted the required
current_password fill and used passwords below the zxcvbn strength
threshold (score 1 < MIN_PASSWORD_STRENGTH=2).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/porchlight/templates/manage/credentials.html

@@ -38,7 +38,8 @@
         {% else %}
         <p>No password set.</p>
         {% endif %}
-        <form hx-post="/manage/credentials/password" hx-target="#password-section" hx-swap="innerHTML">
+        <div id="password-error"></div>
+        <form hx-post="/manage/credentials/password" hx-target="#password-error" hx-swap="innerHTML">
             <input type="hidden" name="csrf_token" value="{{ csrf_token_processor(request) }}">
             {% if has_password %}
             <div>

tests/e2e/credentials.spec.js

@@ -42,6 +42,7 @@ test.describe('Credentials page', () => {
 
   test.describe('Password validation', () => {
     test('shows mismatch error', async ({ page }) => {
+      await page.fill('#current_password', fixtures.cred_password);
       await page.fill('#password', 'newpassword1');
       await page.fill('#confirm', 'newpassword2');
       await page.click('#password-section button[type="submit"]');
@@ -51,6 +52,23 @@ test.describe('Credentials page', () => {
       await expect(alert).toContainText('do not match');
     });
 
+    test('keeps the password form visible after a validation error', async ({ page }) => {
+      await page.fill('#current_password', fixtures.cred_password);
+      await page.fill('#password', 'newpassword1');
+      await page.fill('#confirm', 'newpassword2');
+      await page.click('#password-section button[type="submit"]');
+
+      const alert = page.locator('#password-section [role="alert"]');
+      await expect(alert).toBeVisible({ timeout: 5000 });
+
+      // Regression: the form and its inputs must NOT disappear on error.
+      await expect(page.locator('#password')).toBeVisible();
+      await expect(page.locator('#confirm')).toBeVisible();
+      await expect(
+        page.locator('#password-section button[type="submit"]'),
+      ).toBeVisible();
+    });
+
     test('password input has minlength="8"', async ({ page }) => {
       await expect(page.locator('#password')).toHaveAttribute('minlength', '8');
     });
@@ -62,8 +80,9 @@ test.describe('Credentials page', () => {
 
   test.describe('Password change', () => {
     test('succeeds with matching passwords', async ({ page }) => {
-      await page.fill('#password', 'newpassword123');
+      await page.fill('#current_password', fixtures.cred_password);
-      await page.fill('#confirm', 'newpassword123');
+      await page.fill('#password', 'purple-tiger-mountain-42');
+      await page.fill('#confirm', 'purple-tiger-mountain-42');
       await page.click('#password-section button[type="submit"]');
 
       const status = page.locator('#password-section [role="status"]');

tests/e2e/full-flow.spec.js

@@ -30,8 +30,8 @@ test.describe('Full user journey', () => {
     await expect(passwordInput).toBeVisible();
     await expect(confirmInput).toBeVisible();
 
-    await passwordInput.fill('mypassword123');
+    await passwordInput.fill('purple-tiger-mountain-42');
-    await confirmInput.fill('mypassword123');
+    await confirmInput.fill('purple-tiger-mountain-42');
     await page.click('#password-section button[type="submit"]');
 
     // Wait for success message
@@ -51,7 +51,7 @@ test.describe('Full user journey', () => {
 
     // ---- Step 4: Login with the password we just set ----
     await page.fill('#username', fixtures.register_username);
-    await page.fill('#password', 'mypassword123');
+    await page.fill('#password', 'purple-tiger-mountain-42');
     await page.click('form[hx-post="/login/password"] button[type="submit"]');
 
     // Wait for redirect to credentials page