Prompt suggestions on the new-chat screen

A blank composer is the least helpful thing a chat client can show someone
who has just installed one. Three cards now sit under the empty state, and
an administrator manages them at /admin/suggestions.

Clicking a card fills the composer and stops there. It deliberately does not
send: every default ends mid-sentence, because a card is a starting point
rather than a question somebody already asked, and the caret lands where the
person has to start typing.

Seeding is guarded by a settings flag, not by "is the table empty" --
otherwise an administrator who decided against them would get all three back
on every restart. Capped at twelve, six shown: past a dozen this is a menu,
and a menu on the empty screen is a worse blank page than a blank page.

The cards are gated on there being no chat at all, not on the thread being
empty. An empty chat someone opened on purpose already has a model and a
prompt chosen.

Also fixes a pre-existing bug the position test caught. Both this and
_refresh_models wrote `coalesce(max(position), -1) or -1`, and position 0 is
falsy -- so the second row landed back on 0 on top of the first. The
coalesce was already doing that job; the `or` was undoing it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/web/templates/admin/_layout.html

@@ -47,6 +47,11 @@
           {{ icon("sparkle", "icon--sm") }}
           <span class="nav-item__label">Prompts</span>
         </a>
+        <a class="nav-item {{ 'is-active' if section == 'suggestions' }}"
+           href="/admin/suggestions">
+          {{ icon("star", "icon--sm") }}
+          <span class="nav-item__label">Suggestions</span>
+        </a>
         <a class="nav-item {{ 'is-active' if section == 'users' }}" href="/admin/users">
           {{ icon("user", "icon--sm") }}
           <span class="nav-item__label">Users</span>

src/lembas/web/templates/admin/suggestions.html

@@ -0,0 +1,120 @@
+{% extends "admin/_layout.html" %}
+{% from "_macros.html" import icon %}
+{% set section = "suggestions" %}
+
+{% block title %}Suggestions - LLeMbas{% endblock %}
+{% block heading %}Suggestions{% endblock %}
+
+{% block admin_content %}
+<p class="admin-lede">
+  Cards on the new-chat screen. Clicking one puts its prompt in the composer
+  without sending it — the built-in ones deliberately end mid-sentence, so the
+  caret lands where the person has to start typing. The first
+  {{ max_shown }} enabled ones are shown, in this order.
+</p>
+
+{% if saved %}
+<div class="alert alert--success">{{ icon("check", "icon--sm") }} <span>{{ saved }}</span></div>
+{% endif %}
+
+{% for suggestion in suggestions %}
+<form class="card" method="post" action="/admin/suggestions/{{ suggestion.id }}">
+  <div class="card__header">
+    <h2 class="card__title">
+      {{ suggestion.name }}
+      {% if not suggestion.enabled %}<span class="badge">hidden</span>{% endif %}
+      {% if loop.index > max_shown and suggestion.enabled %}
+      <span class="badge badge--warning" title="Only the first {{ max_shown }} are shown">
+        below the cut
+      </span>
+      {% endif %}
+    </h2>
+    <button class="btn btn--sm btn--danger" type="submit"
+            formaction="/admin/suggestions/{{ suggestion.id }}/delete"
+            data-confirm-button="Delete the suggestion “{{ suggestion.name }}”?"
+            data-confirm-title="Delete suggestion">
+      {{ icon("trash", "icon--sm") }}
+    </button>
+  </div>
+
+  <div class="grid grid--2">
+    <div class="field">
+      <label class="field__label" for="name-{{ suggestion.id }}">Name</label>
+      <input class="input" id="name-{{ suggestion.id }}" name="name"
+             value="{{ suggestion.name }}" maxlength="120">
+      <p class="field__hint">The heading on the card.</p>
+    </div>
+    <div class="field">
+      <label class="field__label" for="position-{{ suggestion.id }}">Position</label>
+      <input class="input" id="position-{{ suggestion.id }}" name="position" type="number"
+             min="1" value="{{ suggestion.position + 1 }}">
+      <p class="field__hint">Order on the screen, lowest first.</p>
+    </div>
+  </div>
+
+  <div class="field">
+    <label class="field__label" for="description-{{ suggestion.id }}">Description</label>
+    <input class="input" id="description-{{ suggestion.id }}" name="description"
+           value="{{ suggestion.description }}" maxlength="300">
+    <p class="field__hint">One line under the name, saying what it is for.</p>
+  </div>
+
+  <div class="field">
+    <label class="field__label" for="prompt-{{ suggestion.id }}">Prompt</label>
+    <textarea class="textarea" id="prompt-{{ suggestion.id }}" name="prompt"
+              rows="4">{{ suggestion.prompt }}</textarea>
+    <p class="field__hint">
+      Put in the composer, not sent. Ending it mid-sentence is usually right:
+      the person still has to say what they are asking about.
+    </p>
+  </div>
+
+  <div class="field">
+    <label class="checkbox">
+      <input type="checkbox" name="enabled" value="true" {{ 'checked' if suggestion.enabled }}>
+      <span>Show this one</span>
+    </label>
+  </div>
+
+  <div class="card__footer">
+    <button class="btn btn--primary btn--sm" type="submit">Save</button>
+  </div>
+</form>
+{% else %}
+<div class="empty">
+  {{ icon("sparkle", "empty__mark") }}
+  <h2 class="empty__title">No suggestions</h2>
+  <p class="empty__text">The new-chat screen shows its empty state instead.</p>
+</div>
+{% endfor %}
+
+{% if not at_limit %}
+<form class="card" method="post" action="/admin/suggestions">
+  <h2 class="card__title">Add a suggestion</h2>
+  <div class="field">
+    <label class="field__label" for="new-name">Name</label>
+    <input class="input" id="new-name" name="name" maxlength="120"
+           placeholder="Summarise a document" required>
+  </div>
+  <div class="field">
+    <label class="field__label" for="new-description">Description</label>
+    <input class="input" id="new-description" name="description" maxlength="300"
+           placeholder="What it is for, in one line.">
+  </div>
+  <div class="field">
+    <label class="field__label" for="new-prompt">Prompt</label>
+    <textarea class="textarea" id="new-prompt" name="prompt" rows="4"
+              placeholder="What lands in the composer when the card is clicked."></textarea>
+  </div>
+  <div class="card__footer">
+    <button class="btn btn--primary" type="submit">Add</button>
+  </div>
+</form>
+{% else %}
+<p class="admin-lede">
+  {{ max_suggestions }} is the limit. Delete one to add another — past a dozen
+  this is a menu, and a menu on the empty screen is a worse blank page than a
+  blank page.
+</p>
+{% endif %}
+{% endblock %}