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/loopd/tests/tools.rs

@@ -3,10 +3,10 @@
 
 mod support;
 
+use bxcore::{CallId, DenyReason, SessionId, ToolRequest, ToolResponse};
 use loopd::tools::{
     Dispatch, FakeTools, Pending, Registry, ToolPort, cap_result, denial_text, dispatch,
 };
-use proto::{CallId, DenyReason, SessionId, ToolRequest, ToolResponse};
 
 fn req(tool: &str, arguments: &str) -> ToolRequest {
     ToolRequest {
@@ -125,10 +125,10 @@ fn any_other_tool_goes_to_the_port_as_it_is() {
 fn the_clock_is_answered_locally_whatever_its_arguments() {
     for registry in [Registry::m2b(), Registry::m3a(), Registry::new(vec![])] {
         for arguments in ["{}", r#"{"zone":"UTC"}"#, "not json", ""] {
-            let before = proto::Timestamp::now();
+            let before = bxcore::Timestamp::now();
             match dispatch(&registry, "clock", arguments) {
                 Dispatch::Local(text) => {
-                    let time = proto::Timestamp::parse(&text)
+                    let time = bxcore::Timestamp::parse(&text)
                         .unwrap_or_else(|e| panic!("an RFC 3339 time, got {text:?}: {e:?}"));
                     assert!(time >= before, "{text}");
                     assert!(text.ends_with('Z'), "UTC: {text}");
@@ -283,7 +283,7 @@ fn fake_tools_answer_echo_deny_the_rest_and_record_calls() {
             truncated,
         } => {
             assert_eq!(content, "box");
-            assert_eq!(class, proto::DataClass::Public);
+            assert_eq!(class, bxcore::DataClass::Public);
             assert!(!untrusted && !truncated);
         }
         other => panic!("{other:?}"),