Track 3: read-only source preview (vet a feed before adding)

- feeds.preview_feed(): fetch + score a sample WITHOUT persisting; returns
  freshness, acceptance rate, cortisol/ragebait/PR averages, and example
  accepted/rejected items. With an LLM client it also returns topic/flavor mix
  and the model's (accurate) acceptance view.
- CLI 'preview-source URL [--sample] [--classify]'.
- API 'GET /api/source-preview?url=&sample=&classify=' with an http(s)-only
  guard (SSRF note left for go-public hardening).
- Site 'Suggest a source' panel with Quick check (heuristic, instant) and Deep
  check (model, accurate), rendered DOM-safely.
- Tests: network-free preview_feed tests via monkeypatched fetch (45 total).
- README documents the command, endpoint, and updated roadmap.

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

goodnews/static/index.html

@@ -88,6 +88,19 @@
     .panel .reset { margin-top: 6px; background: none; border: none; color: var(--muted);
       cursor: pointer; font-size: 0.8rem; text-decoration: underline; }
     .calm-note { color: var(--muted); font-size: 0.8rem; margin: -8px 0 14px; }
+    .addsource { background: var(--card); border: 1px solid var(--line); border-radius: 12px;
+      padding: 16px 18px; margin-bottom: 18px; }
+    .addsource .hint { color: var(--muted); font-size: 0.82rem; margin: 0 0 10px; }
+    .addsource-row { display: flex; gap: 8px; flex-wrap: wrap; }
+    .addsource input { flex: 1 1 240px; border: 1px solid var(--line); border-radius: 8px;
+      padding: 7px 11px; font-size: 0.9rem; }
+    .addbtn { border: 1px solid var(--accent); background: var(--accent); color: #fff;
+      border-radius: 8px; padding: 7px 14px; cursor: pointer; font-size: 0.85rem; }
+    .addbtn.ghost { background: none; color: var(--accent); }
+    .preview-metrics { margin-top: 14px; }
+    .preview-metrics .stat { font-size: 0.9rem; margin: 2px 0; }
+    .preview-metrics .label { color: var(--muted); }
+    .preview-metrics ul { margin: 4px 0 10px; padding-left: 18px; font-size: 0.86rem; }
     footer { text-align: center; color: var(--muted); font-size: 0.78rem; padding: 20px; }
     footer a { color: var(--accent); }
   </style>
@@ -130,6 +143,17 @@
     <div id="topic-chips" class="chips"></div>
     <div id="flavor-chips" class="chips"></div>
     <div id="feed"></div>
+
+    <div class="section-title">Suggest a source</div>
+    <div class="addsource">
+      <p class="hint">Paste a feed URL to see how calm it is before anyone adds it. Nothing is saved — this just samples and scores recent items.</p>
+      <div class="addsource-row">
+        <input id="src-url" type="text" placeholder="https://example.com/feed/" />
+        <button id="src-quick" class="addbtn">Quick check</button>
+        <button id="src-deep" class="addbtn ghost">Deep check (uses model)</button>
+      </div>
+      <div id="src-result"></div>
+    </div>
   </main>
   <footer>
     goodNews · metadata &amp; links only, no stored articles ·
@@ -354,6 +378,11 @@
       fc.appendChild(chip("all", true, () => setFlavor(null)));
       cats.flavors.forEach(f => fc.appendChild(chip(f.key, false, () => setFlavor(f.key))));
 
+      // source preview controls
+      el("src-quick").onclick = () => previewSource(false);
+      el("src-deep").onclick = () => previewSource(true);
+      el("src-url").addEventListener("keydown", (e) => { if (e.key === "Enter") previewSource(false); });
+
       // panel controls
       el("calm-toggle").onclick = () => el("panel").classList.toggle("open");
       el("term-add").onclick = addTerm;
@@ -363,6 +392,56 @@
       refreshAll();
     }
 
+    async function previewSource(deep) {
+      const url = el("src-url").value.trim();
+      const out = el("src-result");
+      out.replaceChildren();
+      if (!/^https?:\/\//i.test(url)) {
+        out.append(node("div", "empty", "Enter a URL starting with http:// or https://"));
+        return;
+      }
+      out.append(node("div", "empty", deep ? "Deep checking with the model — this can take a moment…" : "Checking…"));
+      try {
+        const p = await getJSON(`/api/source-preview?url=${encodeURIComponent(url)}&classify=${deep}`);
+        renderPreview(out, p);
+      } catch (e) {
+        out.replaceChildren(node("div", "empty", "Could not read that feed."));
+      }
+    }
+
+    function renderPreview(out, p) {
+      out.replaceChildren();
+      const box = node("div", "preview-metrics");
+      const stat = (label, value) => {
+        const d = node("div", "stat");
+        d.append(node("span", "label", label + " "));
+        d.append(document.createTextNode(String(value)));
+        box.append(d);
+      };
+      stat("Mode:", p.classified ? "model (accurate)" : "heuristic (quick, conservative)");
+      stat("Acceptance:", `${Math.round(p.acceptance_rate * 100)}% (${p.accepted}/${p.sampled})`);
+      stat("Freshness:", `${p.recent_7d}/${p.sampled} in last 7 days · newest ${(p.newest_published||"unknown").slice(0,10)}`);
+      stat("Calm averages:", `cortisol ${p.avg_cortisol} · ragebait ${p.avg_ragebait} · PR ${p.avg_pr_risk}`);
+      const mix = (m) => Object.entries(m).map(([k, v]) => `${k} ${v}`).join(" · ") || "—";
+      if (p.classified) {
+        stat("Topics:", mix(p.topic_mix));
+        stat("Flavors:", mix(p.flavor_mix));
+      }
+      if (p.examples_accepted.length) {
+        box.append(node("div", "stat label", "Would surface:"));
+        const ul = node("ul");
+        p.examples_accepted.forEach(t => ul.append(node("li", null, t)));
+        box.append(ul);
+      }
+      if (p.examples_rejected.length) {
+        box.append(node("div", "stat label", "Would skip:"));
+        const ul = node("ul");
+        p.examples_rejected.forEach(e => ul.append(node("li", null, e.title)));
+        box.append(ul);
+      }
+      out.append(box);
+    }
+
     function addTerm() {
       const v = el("term-input").value.trim();
       if (v && !prefs.avoid_terms.includes(v)) { prefs.avoid_terms.push(v); savePrefs(); }