Add case_precedents: attached legal support for the compose phase

New self-contained table + MCP tools + FastAPI endpoints for letting
the chair attach external case-law quotes (quote + citation מראה מקום,
optional chair note, optional archived PDF) to either a specific
threshold_claim / issue or the case as a whole.

Data model
  - case_precedents (SCHEMA_V5_SQL) — case_id, section_id NULL/
    "threshold_N"/"issue_N", quote, citation (free-text), chair_note,
    pdf_document_id FK to documents, denormalized practice_area for
    cross-case library filtering.
  - Deliberately NOT linked to the existing case_law table — that one
    has UNIQUE(case_number) which would force parsing the free-text
    citation into a structured key. A backfill pass into case_law is
    a later follow-up once the UI stabilizes.
  - db.py gains 4 helpers: create_case_precedent, list_case_precedents,
    delete_case_precedent, search_precedent_library. The last uses
    DISTINCT ON (citation) for the cross-case typeahead so each
    precedent appears once even if reused across many cases.

MCP tools (legal_mcp/tools/precedents.py)
  - precedent_attach, precedent_list, precedent_remove,
    precedent_search_library — registered in server.py.

FastAPI (web/app.py)
  - POST /api/cases/{n}/precedents — create, with PrecedentCreateRequest
  - POST /api/cases/{n}/precedents/upload-pdf — one-shot PDF upload to
    a dedicated documents/precedents/ subdirectory, creates a
    documents row with doc_type="precedent_archive" and no text
    extraction (archive only)
  - GET /api/cases/{n}/precedents — list
  - DELETE /api/precedents/{id} — uses path param since precedent_id
    is a UUID (slash-safe, unlike case numbers)
  - GET /api/precedents/search?q=...&practice_area=... — library
    typeahead

Block-writer integration into _build_precedents_context is a deferred
follow-up — Phase 1 surfaces the feature in the compose UI only.

Plan: ~/.claude/plans/woolly-cooking-graham.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/server.py

@@ -45,7 +45,9 @@ mcp = FastMCP(
 
 # ── Import and register tools ───────────────────────────────────────
 
-from legal_mcp.tools import cases, documents, search, drafting, workflow  # noqa: E402
+from legal_mcp.tools import (  # noqa: E402
+    cases, documents, search, drafting, workflow, precedents,
+)
 
 
 # Case management
@@ -108,6 +110,42 @@ async def case_delete(case_number: str, remove_files: bool = False) -> str:
     return await cases.case_delete(case_number, remove_files)
 
 
+# Precedent attachments (user-supplied legal support for the compose phase)
+@mcp.tool()
+async def precedent_attach(
+    case_number: str,
+    quote: str,
+    citation: str,
+    section_id: str = "",
+    chair_note: str = "",
+    pdf_document_id: str = "",
+) -> str:
+    """צירוף פסיקה תומכת לתיק. section_id ריק = כללי לתיק; אחרת threshold_1/issue_3."""
+    return await precedents.precedent_attach(
+        case_number, quote, citation, section_id, chair_note, pdf_document_id,
+    )
+
+
+@mcp.tool()
+async def precedent_list(case_number: str) -> str:
+    """רשימת כל הפסיקות שצורפו לתיק."""
+    return await precedents.precedent_list(case_number)
+
+
+@mcp.tool()
+async def precedent_remove(precedent_id: str) -> str:
+    """הסרת פסיקה מצורפת."""
+    return await precedents.precedent_remove(precedent_id)
+
+
+@mcp.tool()
+async def precedent_search_library(
+    query: str, practice_area: str = "", limit: int = 10,
+) -> str:
+    """חיפוש בספרייה הרוחבית של ציטוטים שנצברו בין תיקים."""
+    return await precedents.precedent_search_library(query, practice_area, limit)
+
+
 # Documents
 @mcp.tool()
 async def document_upload(