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/turn.rs

@@ -6,8 +6,8 @@ mod support;
 #[path = "support/turn.rs"]
 mod turn_support;
 
+use bxcore::{DataClass, LogRecord, SessionId, ToolResponse, TurnEvent};
 use loopd::tools::Registry;
-use proto::{DataClass, LogRecord, SessionId, ToolResponse, TurnEvent};
 use support::{Reply, ok_result};
 use turn_support::{setup, types};
 
@@ -102,7 +102,7 @@ fn a_tool_turn_goes_through_the_port_and_records_everything() {
         "arguments are passed on unparsed"
     );
     assert_eq!(calls[0].session, SessionId::new("a").unwrap());
-    assert_eq!(calls[0].call, proto::CallId(1));
+    assert_eq!(calls[0].call, bxcore::CallId(1));
 
     match &session.records()[4] {
         LogRecord::ToolResult {
@@ -114,7 +114,7 @@ fn a_tool_turn_goes_through_the_port_and_records_everything() {
             truncated,
             ..
         } => {
-            assert_eq!(*call, proto::CallId(1));
+            assert_eq!(*call, bxcore::CallId(1));
             assert_eq!(
                 tool_call_id, "wgE8iFI58Zni4WCTiCMNp4TzCcM8ou7F",
                 "the server's id, so the template can pair it"