P2 slice 5: files in and out

Files reach the books through the server: uploads by hash and size,
then filed; exports (the CPA package, the 1099 worksheet, W-9s) handed
over as downloads from the server, never read off disk by the agent.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-mcp/src/scopes.rs

@@ -119,7 +119,7 @@ pub const TABLE: [(&str, Needs); 109] = [
     ("books.assign_role", P),
     ("books.set_tax_category", W),
     ("books.import_chart_csv", W),
-    ("books.import_local_file", W),
+    ("books.begin_upload", W),
     ("books.export", R),
     ("books.register_asset", W),
     ("books.asset_schedule", R),