Rebuild Arti from audited source with enforced provenance

Vendored arti.xcframework rebuilt from source (Rust 1.96.0, normalized
archive metadata for reproducible hashes). New ARTI-BINARY-PROVENANCE.md
records toolchain, rebuild steps, and a SHA256 manifest for every file
in the xcframework. A new CI workflow turns that policy into a gate:
PRs must keep the binary matching the manifest, and binary changes must
ship with source/lockfile/build-script evidence.

Also raises TorManager.awaitReady's default timeout from 25s to 75s to
match the bootstrap monitor deadline - a shorter wait reported "not
ready" while Arti was still legitimately bootstrapping, silently
stranding queued relay work.

Privacy policy, Tor integration doc, and privacy assessment updated to
match the current implementation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

localPackages/Arti/arti-bitchat/Cargo.toml

@@ -2,7 +2,7 @@
 name = "arti-bitchat"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.86"
+rust-version = "1.90"
 
 [lib]
 crate-type = ["staticlib"]