feat(kb): split-view PDF jump-to-page for both ask and search modes

Search and ask modes now render results as a two-column layout: a left
column with ranked hit cards (search) or Shira's answer + source picker
(ask), and a right column with an iframe showing the source PDF scrolled
to page_number. Clicking a hit (search) or source pill (ask) swaps the
iframe's src, so users can verify a quote against the original PDF
without leaving the KB tab.

- search: renderSearchResults lays out results as panel cards on the
  left (with kind + title + section + "עמ׳ N" label); the top hit is
  pre-selected and its PDF loads on the right. Clicking any card
  re-highlights it and swaps the preview. Law-kind hits (Wikisource
  text) gracefully fall back to a chunk-text panel with a Wikisource
  link so the right pane never 404s on a text source.
- ask: renderAskAnswer dedups /kb/ask's sources[] by source_id,
  collects all cited pages per source, and renders a picker row plus
  per-source page-jump buttons. First source's first page loads on
  initial render; buttons swap the iframe without re-running the query.

Depends on shira-hermes commits e534709 + 1ca1cc0 (chunker page_number
propagation + null-byte strip) — without them, every PDF collapses to
page 1 in the DB and the jump links are cosmetic.

Refs Task Master #1

.taskmaster/tasks/tasks.json

@@ -0,0 +1,35 @@
+{
+  "master": {
+    "tasks": [
+      {
+        "id": 1,
+        "title": "feat: search-mode split-view with PDF + page jump",
+        "description": "Render /kb/search results as a two-column split view: left column is the stack of ranked hit cards (kind, title, section, page label), right column is an iframe viewing the selected hit's PDF scrolled to page_number. Clicking any hit swaps the iframe. Text-only sources (law from Wikisource) fall back to a chunk/text panel with a Wikisource link so the right column never 404s.",
+        "status": "in-progress",
+        "priority": "high",
+        "details": "Before this change renderSearchResults produced plain vertical text cards — users got the chunk body and had to open the Wikisource link (or track down the PDF manually) to verify context. With 5 of 5 PDFs now carrying accurate page_number (shira-hermes e534709 + 1ca1cc0), the search UI can finally deep-link to the right page. Mirrors the ask-mode split view (v0.1.7 uncommitted).",
+        "testStrategy": "Search 'תקנה 37' → first hit should be a regulation/circular → right pane loads the PDF at page ~N where the section appears. Click a lower-ranked law hit → right pane swaps to a Wikisource link view. Search 'הגדרות' → hits span multiple sources → each click swaps iframe source.",
+        "subtasks": [],
+        "dependencies": [],
+        "createdAt": "2026-04-24T15:47:00Z"
+      },
+      {
+        "id": 2,
+        "title": "fix(kb/chunker): page_number propagation through split + packing (shira-hermes)",
+        "description": "Applied in shira-hermes commits e534709 + 1ca1cc0: (1) _split_oversized now re-derives page_number per piece from markers embedded in parent content + a virtual (offset 0, parent.page_number) anchor, (2) chunk_circular tracks absolute paragraph offsets in the original text so each packed sub-chunk reports its real starting page, (3) _as_dicts strips stray \\x00 bytes left behind when _split_oversized slices through a marker sentinel. Reference data: ספר הליקויים now 211 chunks × 210 pages (1-413) vs 209 × 1 before. Not work for this repo, but the search split-view in task #1 depends on it.",
+        "status": "done",
+        "priority": "high",
+        "details": "Lives in espocrm-extensions/shira-hermes. Logged here for traceability because task #1 can't demonstrate correct page jumps without it.",
+        "testStrategy": "Query DB: SELECT source_id, MIN/MAX(page_number), COUNT(DISTINCT page_number) FROM kb_chunk GROUP BY source_id — every PDF source should span multiple distinct pages.",
+        "subtasks": [],
+        "dependencies": [],
+        "createdAt": "2026-04-24T15:47:00Z"
+      }
+    ],
+    "metadata": {
+      "created": "2026-04-24T15:47:00Z",
+      "updated": "2026-04-24T15:47:00Z",
+      "description": "KnowledgeBase extension tasks"
+    }
+  }
+}