proto becomes bxcore, the one shared crate (M5b task 00)

Done the way the owner asked and the spike mapped: the crate and the
manifests renamed, then what the build reported fixed. Layers: 138
"proto unresolved" errors across 169 files; cargo fmt reordering
imports; six fixture paths built as strings in brokerd's and bxctl's
tests, which the compiler cannot see, and comments naming
crates/proto/; the crate-dependency check and its self-test. One more
the spike did not reach: a `\nproto =` key inside a printf format in
the self-test, which a word-boundary replacement skips because `n` and
`p` are both word characters.

make gate: gate: ok, 944 tests; no new entry in /tmp.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/brokerd/tests/grants.rs

@@ -7,7 +7,7 @@
 mod tmp;
 
 use brokerd::grants::{GrantSet, LoadedGrant, RUNBOOK, load, render, valid_id};
-use proto::{Constraints, DataClass, Grant, GrantProblem, Hash32, Mode};
+use bxcore::{Constraints, DataClass, Grant, GrantProblem, Hash32, Mode};
 use std::path::{Path, PathBuf};
 use tmp::TempDir;
 
@@ -66,8 +66,8 @@ fn the_valid_fixture_loads_in_id_order_with_file_hashes() {
     assert!(!notes.grant.untrusted);
     assert_eq!(notes.grant.constraints.paths, ["/home/kyle/notes"]);
     let bytes = std::fs::read(fixture("valid").join("notes-read.toml")).unwrap();
-    assert_eq!(notes.sha256, proto::sha256(&bytes).unwrap());
-    // Defaults from `proto::Grant`.
+    assert_eq!(notes.sha256, bxcore::sha256(&bytes).unwrap());
+    // Defaults from `bxcore::Grant`.
     let scratch = &set.grants()[3];
     assert_eq!(scratch.grant.result_class, DataClass::Private);
     assert!(scratch.grant.untrusted);