feat(catalog-config): mirror manifest v2 schema in validator + site

Phase D of v2.3 template configuration — closes the loop between the
Swift app and the catalog pipeline. Authors can now ship schemaful
bundles; the Python validator enforces the same invariants the Swift
installer does; the catalog site displays the schema so visitors see
what they'll need to configure before installing.

Python validator (tools/build-catalog.py):
- SUPPORTED_SCHEMA_VERSIONS accepts both 1 and 2 (v1 bundles are
  unchanged; v2 adds optional manifest.config).
- New _validate_config_schema function mirrors the Swift
  ProjectConfigService.validateSchema rules: unique keys, supported
  types, enum option presence + unique values, list itemType ==
  "string", secret-field cannot declare a default,
  modelRecommendation.preferred non-empty when present.
- _validate_contents_claim cross-checks contents.config (field count)
  against config.schema actual length — mismatch refused.
- TemplateRecord.to_catalog_entry exposes `config` in catalog.json so
  the site can render the schema.
- render_site copies each bundle's template.json to the detail dir as
  manifest.json (only when the manifest has a config block — keeps
  the served tree lean and makes "no manifest.json" a meaningful
  404 signal in the frontend).
- catalog.json's own schemaVersion stays at 1 (independent of per-
  template manifest schemaVersion).

Python tests (tools/test_build_catalog.py): 8 new cases in a new
ConfigSchemaValidationTests suite — accepts schemaful bundle, rejects
duplicate keys, rejects secret-with-default, rejects enum-without-
options, rejects unsupported field type, rejects contents.config
count mismatch, rejects unsupported list itemType, legacy v1
manifests pass unchanged. 24/24 Python tests total.

Site (site/widgets.js):
- New renderConfigSchema(container, config) — mirrors the display
  on the Scarf install preview. Renders each field as a <dt>/<dd>
  pair with type + required badges; enum shows choice labels; list
  fields show min/max bounds; string fields show pattern/length;
  secret fields get a "Stored in Keychain" reassurance. Optional
  modelRecommendation panel at the bottom with preferred + rationale
  + alternatives.
- The renderer is display-only — the site never collects values;
  that's the Scarf app's job.

template.html.tmpl adds a #config-schema <section>. The inline script
fetches manifest.json from the detail dir; on success hands the
config block to ScarfWidgets.renderConfigSchema; on 404 (schema-less
templates) silently leaves the section empty. CSS in styles.css
adds a config-schema panel matching the accent-green aesthetic.

24/24 Python + 50/50 Swift tests pass. site-status-checker still
renders correctly (schema-less; manifest.json isn't copied for it).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

site/widgets.js

@@ -408,12 +408,116 @@
       .replace(/'/g, "'");
   }
 
+  // ---------------------------------------------------------------------
+  // Config-schema display (v2.3 — template configuration).
+  // ---------------------------------------------------------------------
+  //
+  // Renders the author-declared schema as a read-only listing on the
+  // catalog detail page. The site itself never collects values — the
+  // form UI lives inside the Scarf app. This is purely informational
+  // so visitors know what they'll need to fill in before installing.
+
+  /**
+   * Render a manifest.config block into `container` as a summary.
+   * Safe to call with a null schema (no-op).
+   * @param {HTMLElement} container
+   * @param {{schema: Array, modelRecommendation?: object} | null | undefined} config
+   */
+  function renderConfigSchema(container, config) {
+    container.innerHTML = "";
+    if (!config || !Array.isArray(config.schema) || config.schema.length === 0) {
+      return;
+    }
+    const wrap = elt("div", "config-schema");
+    const header = elt("h3", "config-schema-header", "Configuration");
+    wrap.appendChild(header);
+    const desc = elt("p", "config-schema-desc",
+      "Fields you'll fill in during install. Secrets are stored in the macOS Keychain; non-secret values live at <project>/.scarf/config.json.");
+    wrap.appendChild(desc);
+
+    const list = elt("dl", "config-schema-list");
+    for (const field of config.schema) {
+      const dt = elt("dt", "config-field-header");
+      dt.appendChild(elt("span", "config-field-key", field.key || ""));
+      dt.appendChild(elt("span", "config-field-type", field.type || ""));
+      if (field.required) {
+        const req = elt("span", "config-field-required", "required");
+        dt.appendChild(req);
+      }
+      list.appendChild(dt);
+
+      const dd = elt("dd", "config-field-body");
+      if (field.label) {
+        dd.appendChild(elt("div", "config-field-label", field.label));
+      }
+      if (field.description) {
+        const descEl = elt("div", "config-field-description");
+        descEl.innerHTML = renderInline(field.description);
+        dd.appendChild(descEl);
+      }
+      const constraint = summariseConstraint(field);
+      if (constraint) {
+        dd.appendChild(elt("div", "config-field-constraint", constraint));
+      }
+      list.appendChild(dd);
+    }
+    wrap.appendChild(list);
+
+    if (config.modelRecommendation) {
+      const rec = config.modelRecommendation;
+      const recBlock = elt("div", "config-model-rec");
+      recBlock.appendChild(elt("div", "config-model-label", "Recommended model"));
+      recBlock.appendChild(elt("div", "config-model-preferred", rec.preferred || ""));
+      if (rec.rationale) {
+        recBlock.appendChild(elt("div", "config-model-rationale", rec.rationale));
+      }
+      if (Array.isArray(rec.alternatives) && rec.alternatives.length > 0) {
+        recBlock.appendChild(elt("div", "config-model-alternatives",
+          "Also works: " + rec.alternatives.join(", ")));
+      }
+      wrap.appendChild(recBlock);
+    }
+
+    container.appendChild(wrap);
+  }
+
+  /** One-line human summary of a field's type-specific constraints.
+   * Empty string if nothing noteworthy to say. */
+  function summariseConstraint(field) {
+    const type = field.type;
+    if (type === "enum") {
+      const opts = Array.isArray(field.options) ? field.options : [];
+      const values = opts.map(o => o && o.label ? o.label : (o && o.value) || "").filter(Boolean);
+      if (values.length > 0) return "Choices: " + values.join(", ");
+    } else if (type === "list") {
+      const min = field.minItems, max = field.maxItems;
+      if (min && max) return `${min}–${max} items`;
+      if (min) return `At least ${min} item${min === 1 ? "" : "s"}`;
+      if (max) return `At most ${max} item${max === 1 ? "" : "s"}`;
+    } else if (type === "string" || type === "text") {
+      if (field.pattern) return `Pattern: ${field.pattern}`;
+      const min = field.minLength, max = field.maxLength;
+      if (min && max) return `${min}–${max} characters`;
+      if (min) return `At least ${min} characters`;
+      if (max) return `At most ${max} characters`;
+    } else if (type === "number") {
+      const min = field.min, max = field.max;
+      if (min !== undefined && max !== undefined) return `${min}–${max}`;
+      if (min !== undefined) return `≥ ${min}`;
+      if (max !== undefined) return `≤ ${max}`;
+    } else if (type === "secret") {
+      return "Stored in the macOS Keychain on install — never in git, never in config.json.";
+    }
+    return "";
+  }
+
   // ---------------------------------------------------------------------
   // Public API
   // ---------------------------------------------------------------------
 
   global.ScarfWidgets = {
     renderDashboard,
-    renderMarkdown,   // exposed for the template detail page's README block
+    renderMarkdown,      // used by the detail page's README block
+    renderConfigSchema,  // used by the detail page's Configuration block
   };
 })(typeof window !== "undefined" ? window : this);