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/bxctl/tests/admin.rs

@@ -3,14 +3,14 @@
 
 mod support;
 
+use bxcore::{
+    Approve, DecisionRecord, DenyReason, Empty, Envelope, ErrorCode, GrantProblem, GrantsReport,
+    Message, PROTOCOL_VERSION, Refuse,
+};
 use bxctl::admin::{
     AdminError, cmd_approvals, cmd_approve, cmd_grants_check, cmd_refuse, list, reason_name,
     request, write_block,
 };
-use proto::{
-    Approve, DecisionRecord, DenyReason, Empty, Envelope, ErrorCode, GrantProblem, GrantsReport,
-    Message, PROTOCOL_VERSION, Refuse,
-};
 use std::process::Command;
 use support::{brokerd_with, fake_brokerd, fake_brokerd_frames, pending, ts, wire_error};
 
@@ -140,7 +140,7 @@ fn reason_names_are_the_wire_names() {
 
 // ---- the block ----
 
-fn block(item: &proto::PendingApproval, now: &str) -> String {
+fn block(item: &bxcore::PendingApproval, now: &str) -> String {
     let mut out = Vec::new();
     write_block(&mut out, item, ts(now)).unwrap();
     text(out)
@@ -190,7 +190,7 @@ fn a_session_id_longer_than_ten_characters_is_cut_to_nine_and_an_ellipsis() {
         ("abcdefghij", "session abcdefghij  "),
         ("abcdefghijk", "session abcdefghi…  "),
     ] {
-        item.session = proto::SessionId::new(id).unwrap();
+        item.session = bxcore::SessionId::new(id).unwrap();
         let got = block(&item, "2026-09-18T12:00:00.000Z");
         assert!(got.contains(shown), "{id}: {got}");
     }
@@ -199,7 +199,7 @@ fn a_session_id_longer_than_ten_characters_is_cut_to_nine_and_an_ellipsis() {
 #[test]
 fn taint_is_the_wire_name() {
     let mut item = pending(41, "shell", "{}");
-    item.taint = proto::DataClass::Secret;
+    item.taint = bxcore::DataClass::Secret;
     assert!(block(&item, "2026-09-18T12:00:00.000Z").contains("  taint secret\n"));
 }