feat: Stage C — RAG advanced (#33, #47, #48, #49, #50, #51)

Six independent sub-tasks dispatched in parallel; aggregated here.

## #33 — Hide case_name column
library-list-panel.tsx: `<TableHead>` + `<TableCell>` for "שם"
get `className="hidden"` in both Court and Committee row variants.
DB column preserved for future use.

## #47 — Audit script periodic
New scripts/audit_corpus_integrity.py — 3 SQL checks (external+ערר
prefix, internal missing chair/district, cases.practice_area enum)
+ CEO wakeup on violations + cron `0 7 * * *`. First run: 0 issues.

## #48 — Parent-doc retrieval (gated, default off)
Schema V17: precedent_chunks.parent_chunk_id + chunk_role
('child'|'parent'). New chunker.chunk_document_hierarchical() —
section-aware parents (~1500 tokens) containing ~5 overlapping
children (~300 tokens each). New db.store_precedent_chunks_hierarchical
two-pass writer. Search SQL (semantic + lexical) LEFT-JOIN parent and
swap content + dedupe by parent_chunk_id when flag on. Toggle:
PARENT_DOC_RETRIEVAL_ENABLED + PARENT_DOC_{CHILD,PARENT}_SIZE_TOKENS.
Backfill ~3min and ~$0.20 — deferred to follow-up.

## #49 — Multimodal backfill
New scripts/backfill_multimodal_precedents.py with token-matching
case_number ↔ source files (PDF + DOCX via PyMuPDF). Ran in container:
26 precedents embedded, 503 pages, $0.21, 0 errors. precedent_image_embeddings
grew 3 → 29 rows. 44 remaining are style_corpus-migrated rows (no
source file on disk) — will catch up when re-uploaded.

## #50 — Closed-loop feedback + nDCG
Schema V18: search_logs + search_relevance_feedback. New telemetry.py
with fire-and-forget log_search_bg (p50 = 0.002ms — zero overhead) +
auto-infer_relevance_from_citations (reads case drafts → marks score=3
when cited precedent appears in past search top-K). Hooks added to 5
search paths. scripts/compute_ndcg.py for aggregation. Two admin API
endpoints (GET /api/admin/rag-metrics + POST .../infer). Dashboard UI
deferred — API is enough for now.

## #51 — Halacha quality monitoring
New scripts/monitor_halacha_quality.py — baseline avg confidence
(trusted=0.849, all=0.833, pending=0.694) with rolling window drift
detection. Default 5% threshold. Exits non-zero on alert for cron
integration. Recommended: `0 8 * * 1` weekly Mon 8am.

## Bonus: 230 unlinked citations → missing_precedents
Bulk-imported 230 distinct unlinked citations from
precedent_internal_citations to missing_precedents.status='open',
party='committee', with notes listing source citers. Top candidate:
ע"א 3213/97 (cited 5x). Total open missing_precedents now 237.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/chunker.py

@@ -1,4 +1,14 @@
-"""Legal document chunker - splits text into sections and chunks for RAG."""
+"""Legal document chunker - splits text into sections and chunks for RAG.
+
+The default :func:`chunk_document` emits a single tier of overlapping
+chunks (legacy single-tier indexing). :func:`chunk_document_hierarchical`
+emits two tiers — small "child" chunks for retrieval matching, plus
+larger "parent" chunks that supply broader context to the LLM (parent-
+doc retrieval, TaskMaster #48). The hierarchical variant lives
+alongside the legacy one so callers can opt in via
+``config.PARENT_DOC_RETRIEVAL_ENABLED`` without breaking existing
+single-tier code paths.
+"""
 
 from __future__ import annotations
 
@@ -162,3 +172,152 @@ def _split_section(text: str, chunk_size: int, overlap: int) -> list[str]:
 def _estimate_tokens(text: str) -> int:
     """Rough token estimate for Hebrew text (~1.5 chars per token)."""
     return max(1, len(text) // 2)
+
+
+# ── Parent-doc retrieval (TaskMaster #48) ────────────────────────────
+# Hierarchical chunker — emits a list of (child, parent) pairs:
+#   * each "child" carries the smaller text used for embedding/search
+#   * each "parent" is shared by ~5 consecutive children (1500/300)
+# The list is FLAT — both parents and children live in the same return
+# list, distinguished by ``role``. A child's ``parent_local_id`` points
+# back to its parent's ``local_id``, so the ingest pipeline can resolve
+# the FK after the parent row is INSERTed and its DB UUID is known.
+#
+# Parents are built FIRST (one window of ``parent_size`` tokens per
+# section, sliding by the parent window — no overlap between parents),
+# then each parent is sub-divided into overlapping children. This keeps
+# the parent boundary aligned with semantic sections (so a "discussion"
+# parent doesn't contain stray "ruling" prose) while still allowing
+# child overlap for recall.
+
+
+@dataclass
+class HierarchicalChunk:
+    """One chunk in the two-tier hierarchy.
+
+    Both children and parents share this shape; ``role`` distinguishes
+    them. Children get an embedding at ingest time; parents do not —
+    they exist only to carry context back to the LLM at retrieval time.
+
+    ``local_id`` is a stable in-batch identifier (sequential int) used
+    only by the ingest pipeline to wire children to their parent's DB
+    UUID after the parent INSERT returns. It is NOT persisted.
+    """
+
+    content: str
+    role: str  # 'child' | 'parent'
+    section_type: str = "other"
+    page_number: int | None = None
+    chunk_index: int = 0
+    local_id: int = -1
+    parent_local_id: int | None = None
+
+
+def chunk_document_hierarchical(
+    text: str,
+    child_size: int = config.PARENT_DOC_CHILD_SIZE_TOKENS,
+    parent_size: int = config.PARENT_DOC_PARENT_SIZE_TOKENS,
+    overlap: int = config.PARENT_DOC_CHILD_OVERLAP_TOKENS,
+    page_offsets: list[int] | None = None,
+) -> list[HierarchicalChunk]:
+    """Split a document into a two-tier (child, parent) hierarchy.
+
+    Returns a flat list where each element is either a parent or a
+    child. Children carry ``parent_local_id`` pointing back to their
+    parent's ``local_id``. Caller (ingest pipeline) must insert parents
+    first, capture their DB UUIDs by ``local_id``, then insert children
+    with the resolved UUID in ``parent_chunk_id``.
+
+    Args:
+        text: full document text.
+        child_size: child chunk size in tokens (≈ 300 by default).
+        parent_size: parent chunk size in tokens (≈ 1500 by default).
+            Parents contain ``parent_size // child_size`` children on
+            average.
+        overlap: child-to-child overlap inside a parent (≈ 50 tokens).
+            Parents themselves do not overlap each other.
+        page_offsets: PDF page offsets for tagging chunks with page #.
+
+    Notes:
+        * Parents respect section boundaries (header detection from
+          :data:`SECTION_PATTERNS`). A "facts" parent will not include
+          "ruling" text.
+        * Empty text returns an empty list.
+        * Both child and parent rows are tagged with the page of their
+          first character.
+    """
+    if not text.strip():
+        return []
+    if child_size <= 0 or parent_size <= 0:
+        raise ValueError("child_size and parent_size must be positive")
+    if child_size > parent_size:
+        raise ValueError("child_size must be <= parent_size")
+
+    sections = _split_into_sections(text)
+    out: list[HierarchicalChunk] = []
+    parent_idx = 0  # global parent ordinal (chunk_index for parents)
+    child_idx = 0   # global child ordinal (chunk_index for children)
+    local_id = 0    # sequential id within this document
+
+    for section_type, section_text in sections:
+        # Step 1: split section into parent-sized windows (no overlap).
+        parent_texts = _split_section(section_text, parent_size, overlap=0)
+        for parent_text in parent_texts:
+            parent_local = local_id
+            local_id += 1
+            parent_chunk = HierarchicalChunk(
+                content=parent_text,
+                role="parent",
+                section_type=section_type,
+                chunk_index=parent_idx,
+                local_id=parent_local,
+                parent_local_id=None,
+            )
+            out.append(parent_chunk)
+            parent_idx += 1
+
+            # Step 2: sub-divide this parent into overlapping children.
+            child_texts = _split_section(parent_text, child_size, overlap)
+            for ch_text in child_texts:
+                ch = HierarchicalChunk(
+                    content=ch_text,
+                    role="child",
+                    section_type=section_type,
+                    chunk_index=child_idx,
+                    local_id=local_id,
+                    parent_local_id=parent_local,
+                )
+                out.append(ch)
+                local_id += 1
+                child_idx += 1
+
+    if page_offsets:
+        _assign_pages_hierarchical(out, text, page_offsets)
+    return out
+
+
+def _assign_pages_hierarchical(
+    chunks: list[HierarchicalChunk],
+    text: str,
+    page_offsets: list[int],
+) -> None:
+    """Page-tag both children and parents.
+
+    Same forward-scan strategy as :func:`_assign_pages` but works on
+    the hierarchical list. Parents may span pages; we tag them with
+    the page of their first character (matches how the multimodal
+    retriever joins on page numbers).
+    """
+    from legal_mcp.services.extractor import page_at_offset
+    pos = 0
+    for c in chunks:
+        idx = text.find(c.content, pos)
+        if idx < 0:
+            idx = text.find(c.content)
+        if idx < 0:
+            continue
+        c.page_number = page_at_offset(idx, page_offsets)
+        # Advance past halfway — children share text with their parent
+        # and with each other (overlap), so a small forward step lets
+        # the next find() still pick up the right occurrence.
+        pos = idx + max(1, len(c.content) // 4)