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

docs/parity.md

@@ -57,8 +57,9 @@ version refuses books from a newer one as newer, not corrupt (rules.md
 B-27); the MCP server fails closed after an internal error, and no input
 reaches one (dates are four-digit years, amounts at most a line's, B-28);
 local files
-are read only from the import roots, never the books, the vault or its
-key; no file with a full TIN is filed into the books (B-26); the agent is
+were read only from the import roots, never the books, the vault or its
+key (P2 slice 5 removed local paths: files now come in as uploads or
+inline bytes); no file with a full TIN is filed into the books (B-26); the agent is
 told the rules in force in a short connect text and a handbook, and no
 agent text points at the books' files, git or the repo.