PWA, one send/stop button, audio in and out, web search as a tool

Four pieces of work.

**Installable.** A manifest carrying the instance name, PWA icons rasterised
from the existing mark at design time, a service worker and a themed offline
page. The worker caches the shell only and bails out on /api/, /auth/, /admin/
and anything accepting text/event-stream -- passing a reply stream through a
worker turns it into one delivery at the end, or nothing. It is served from
GET /sw.js rather than the static mount because a worker's scope is the path it
came from.

**Send and Stop are one button.** They were two, and the hidden one was never
hidden: `.btn` is display: inline-flex, which outranks the browser's own
`[hidden] { display: none }`, so Stop sat permanently beside Send. app.css now
forces the attribute to win -- every control toggled with `hidden` depended on
that -- and the composer renders one button carrying both icons, with ui.js
flipping data-composer-action and the type with it.

**Audio.** Speech to text and text to speech against any OpenAI-shaped
/v1/audio/* endpoint: dictate into the composer, have a reply read out.
Instance settings in Admin, per-reader overrides in Settings, with the voice
list discovered from the server where it offers one. Recorded audio is capped
and never written to disk -- it is not an attachment, it has no owner, and
nothing would ever sweep it.

**Web search, as a tool.** This is the tool loop PLAN.md described as the real
work: one reply is now a bounded sequence of requests rather than one. The model
asks, the tool runs, the result goes back and it is asked again, up to three
rounds. Providers are DuckDuckGo (no setup), SearXNG and Firecrawl.

Two decisions worth stating. Tools are only offered to models flagged `tools`,
because an endpoint without support rejects the whole request rather than
ignoring the array -- the same reason images only reach models flagged
`vision`. And tool results are not replayed as context on the next turn, for the
same reasons reasoning is not: the answer already contains what the model made
of them, and replaying stale results into every later request wastes the window
and reliably sends a small model into a search loop. The sources stay visible in
the transcript instead.

Search results are untrusted third-party text and are treated as such: escaped,
and only http/https URLs rendered as links.

338 tests, ruff clean.

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

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

@@ -0,0 +1,150 @@
+{% extends "admin/_layout.html" %}
+{% from "_macros.html" import icon %}
+{% set section = "search" %}
+
+{% block title %}Web search - LLeMbas{% endblock %}
+{% block heading %}Web search{% endblock %}
+
+{% block admin_content %}
+<p class="admin-lede">
+  Lets a model look things up while it answers. It is offered as a tool the
+  model chooses to call, so nothing changes for a question that does not need
+  it — and it is only offered to models marked as supporting tools, because
+  sending a tool list to one that does not fails the whole request.
+</p>
+
+{% if saved %}
+<div class="alert alert--success">{{ icon("check", "icon--sm") }} <span>Search settings saved.</span></div>
+{% endif %}
+
+<form method="post" action="/admin/search">
+  <section class="card">
+    <h2 class="card__title">
+      Web search
+      {% if values.enabled %}<span class="badge badge--success">on</span>
+      {% else %}<span class="badge">off</span>{% endif %}
+    </h2>
+    <div class="field">
+      <label class="checkbox">
+        <input type="checkbox" name="enabled" value="true" {{ 'checked' if values.enabled }}>
+        <span>Offer web search to models that support tools</span>
+      </label>
+      <p class="field__hint">
+        Who may use it is a permission — <code>tools.web_search</code> under
+        Groups &amp; permissions.
+      </p>
+    </div>
+  </section>
+
+  <section class="card">
+    <h2 class="card__title">Provider</h2>
+    <div class="field">
+      {% for provider in providers %}
+      <label class="checkbox" style="align-items: flex-start">
+        <input type="radio" name="provider" value="{{ provider.key }}"
+               {{ 'checked' if values.provider == provider.key }}>
+        <span>
+          <strong>{{ provider.label }}</strong>
+          {% if not provider.needs_setup %}<span class="badge">no setup</span>{% endif %}
+          <div class="text-xs faint">{{ provider.description }}</div>
+          {% if problems[provider.key] %}
+          <div class="text-xs" style="color: var(--danger)">{{ problems[provider.key] }}</div>
+          {% endif %}
+        </span>
+      </label>
+      {% endfor %}
+    </div>
+
+    <div class="grid grid--3">
+      <div class="field">
+        <label class="field__label" for="max-results">Results per search</label>
+        <input class="input" id="max-results" name="max_results" type="number"
+               min="1" max="20" value="{{ values.max_results }}">
+        <p class="field__hint">A ceiling — a model asking for more gets this.</p>
+      </div>
+      <div class="field">
+        <label class="field__label" for="safesearch">Safe search</label>
+        <select class="select" id="safesearch" name="safesearch">
+          {% for option in safesearch_options %}
+          <option value="{{ option }}" {{ 'selected' if option == values.safesearch }}>
+            {{ option }}
+          </option>
+          {% endfor %}
+        </select>
+      </div>
+      <div class="field">
+        <label class="field__label" for="timeout">Timeout (seconds)</label>
+        <input class="input" id="timeout" name="timeout" type="number"
+               min="5" max="120" step="1" value="{{ values.timeout }}">
+      </div>
+    </div>
+
+    <div class="field">
+      <label class="field__label" for="region">DuckDuckGo region</label>
+      <input class="input" id="region" name="region" maxlength="16"
+             value="{{ values.region }}" placeholder="wt-wt">
+      <p class="field__hint">
+        <code>wt-wt</code> is no region at all. <code>uk-en</code>,
+        <code>de-de</code> and so on bias results to a country.
+      </p>
+    </div>
+  </section>
+
+  <section class="card">
+    <h2 class="card__title">SearXNG</h2>
+    <p class="card__lede">
+      Only used when SearXNG is the chosen provider. Your own instance, so no
+      third party sees the queries.
+    </p>
+    <div class="field">
+      <label class="field__label" for="searxng-base-url">Instance URL</label>
+      <input class="input" id="searxng-base-url" name="searxng_base_url" type="url"
+             value="{{ values.searxng_base_url }}" placeholder="http://127.0.0.1:8888">
+      <p class="field__hint">
+        A stock SearXNG refuses JSON. Add <code>- json</code> under
+        <code>search.formats</code> in its <code>settings.yml</code> and restart
+        it, or every search will fail with that message.
+      </p>
+    </div>
+  </section>
+
+  <section class="card">
+    <h2 class="card__title">Firecrawl</h2>
+    <div class="grid grid--2">
+      <div class="field">
+        <label class="field__label" for="firecrawl-base-url">API URL</label>
+        <input class="input" id="firecrawl-base-url" name="firecrawl_base_url" type="url"
+               value="{{ values.firecrawl_base_url }}"
+               placeholder="https://api.firecrawl.dev">
+        <p class="field__hint">Change only for a self-hosted Firecrawl.</p>
+      </div>
+      <div class="field">
+        <label class="field__label" for="firecrawl-api-key">API key</label>
+        <input class="input" id="firecrawl-api-key" name="firecrawl_api_key" type="password"
+               value="{{ unchanged if masked else '' }}"
+               placeholder="{{ masked or 'fc-...' }}" autocomplete="off">
+        <p class="field__hint">Encrypted at rest. Clear the field to remove it.</p>
+      </div>
+    </div>
+  </section>
+
+  <div class="btn-row"><button class="btn btn--primary" type="submit">Save settings</button></div>
+</form>
+
+<section class="card">
+  <h2 class="card__title">Try it</h2>
+  <p class="card__lede">
+    Runs a real search against the <em>saved</em> settings, which is what a chat
+    would do. Save first if you have just changed something.
+  </p>
+  <div class="row" style="gap: var(--sp-2)">
+    <input class="input" id="test-query" name="query" placeholder="mallorn tree"
+           style="flex: 1">
+    <button class="btn" type="button" hx-post="/admin/search/test"
+            hx-include="#test-query" hx-target="#search-test" hx-swap="outerHTML">
+      {{ icon("search", "icon--sm") }} Search
+    </button>
+  </div>
+  <div id="search-test"></div>
+</section>
+{% endblock %}