fix(retrieval): make decisions findable by name + unhide committee uploads

Root cause of "agent can't find the Agasi decision in the corpus" (CMPA-55):
the decision was fully ingested, but the retrieval layer failed on the
realistic agent query — searching by case name.

- RC-A (#52): lexical tsvector covered only chunk content + halacha text,
  so a bare-name query ("אגסי") matched decisions that *cite* the case, not
  the case itself. Add meta_tsv on case_law(case_name, case_number) (SCHEMA
  V20) and OR it into the lexical halacha/chunk SQL with a match boost, so a
  name/number hit surfaces the case's own rows. Agasi: rank 4 → rank 1.
- RC-B (#53): precedent_library_list hard-defaulted source_kind=external_upload
  and never exposed the param, hiding uploaded ערר/בל"מ (internal_committee)
  decisions. Thread source_kind through service → tool → MCP tool (supports
  'internal_committee' / 'all_committees').
- #54: agent instructions (researcher/analyst/writer) — search-by-name
  protocol: add content/case-number, search both corpora, use all_committees
  before declaring "not in corpus".
- #55: chunker produced tiny fragment chunks ("דיון", "החלטה") from header
  keywords matched mid-sentence. Anchor SECTION_PATTERNS to line start +
  merge sub-min sections; exclude <50-char fragments at query time (484
  existing fragments hidden; full re-chunk tracked as #57).

Tests: scripts/test_retrieval_by_name.py (name ranks case above citer +
substantive regressions); chunker unit checks (0 tiny chunks). New findings
filed as tasks #56 (halacha source_kind leak) and #57 (re-chunk migration).

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

mcp-server/src/legal_mcp/server.py

@@ -201,11 +201,20 @@ async def precedent_library_list(
     precedent_level: str = "",
     source_type: str = "",
     search: str = "",
+    source_kind: str = "external_upload",
     limit: int = 100,
 ) -> str:
-    """רשימת הפסיקה בקורפוס הסמכותי, עם פילטרים."""
+    """רשימת הפסיקה בקורפוס, עם פילטרים.
+
+    source_kind: 'external_upload' (ברירת מחדל — פס"ד בתי משפט) /
+    'internal_committee' (החלטות ועדות ערר ערר/בל"מ שהועלו) /
+    'all_committees' (שתיהן — internal + appeals_committee).
+    החלטות ערר/בל"מ שמעלים נשמרות כ-internal_committee — כדי לראותן
+    ברשימה השתמש ב-source_kind='internal_committee' או 'all_committees'.
+    """
     return await plib.precedent_library_list(
-        practice_area, court, precedent_level, source_type, search, limit,
+        practice_area, court, precedent_level, source_type, search,
+        source_kind, limit,
     )