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/support/audit_dir.rs

@@ -6,7 +6,7 @@ use std::collections::BTreeMap;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicU32, Ordering};
 
-use proto::{AuditEvent, CallId, DataClass, DecisionRecord, SessionId, Timestamp};
+use bxcore::{AuditEvent, CallId, DataClass, DecisionRecord, SessionId, Timestamp};
 
 pub const D1: &str = "2026-09-17.jsonl";
 pub const D2: &str = "2026-09-18.jsonl";
@@ -28,14 +28,14 @@ impl TempDir {
         TempDir { path }
     }
 
-    /// A copy of the fixture log `case` from `crates/proto/tests/fixtures/audit/`. With `only`,
+    /// A copy of the fixture log `case` from `crates/bxcore/tests/fixtures/audit/`. With `only`,
     /// just those files: damage in an older file is not seen by an ordinary start, so tests of
     /// the startup check copy the damaged file alone.
     pub fn case(case: &str, only: Option<&[&str]>) -> TempDir {
         let dir = TempDir::unmade(case);
         std::fs::create_dir_all(&dir.path).unwrap();
         let from = format!(
-            "{}/../proto/tests/fixtures/audit/{case}",
+            "{}/../bxcore/tests/fixtures/audit/{case}",
             env!("CARGO_MANIFEST_DIR")
         );
         let mut copied = 0;
@@ -88,7 +88,7 @@ pub fn denied(call: u64) -> AuditEvent {
         tool: "read_file".to_string(),
         arguments: r#"{"path":"/etc/hosts"}"#.to_string(),
         outcome: DecisionRecord::Denied {
-            reason: proto::DenyReason::NoGrant,
+            reason: bxcore::DenyReason::NoGrant,
         },
         grant: None,
         grant_sha256: None,