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/templates/example_prd.txt

@@ -0,0 +1,47 @@
+<context>
+# Overview  
+[Provide a high-level overview of your product here. Explain what problem it solves, who it's for, and why it's valuable.]
+
+# Core Features  
+[List and describe the main features of your product. For each feature, include:
+- What it does
+- Why it's important
+- How it works at a high level]
+
+# User Experience  
+[Describe the user journey and experience. Include:
+- User personas
+- Key user flows
+- UI/UX considerations]
+</context>
+<PRD>
+# Technical Architecture  
+[Outline the technical implementation details:
+- System components
+- Data models
+- APIs and integrations
+- Infrastructure requirements]
+
+# Development Roadmap  
+[Break down the development process into phases:
+- MVP requirements
+- Future enhancements
+- Do not think about timelines whatsoever -- all that matters is scope and detailing exactly what needs to be build in each phase so it can later be cut up into tasks]
+
+# Logical Dependency Chain
+[Define the logical order of development:
+- Which features need to be built first (foundation)
+- Getting as quickly as possible to something usable/visible front end that works
+- Properly pacing and scoping each feature so it is atomic but can also be built upon and improved as development approaches]
+
+# Risks and Mitigations  
+[Identify potential risks and how they'll be addressed:
+- Technical challenges
+- Figuring out the MVP that we can build upon
+- Resource constraints]
+
+# Appendix  
+[Include any additional information:
+- Research findings
+- Technical specifications]
+</PRD>