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/support/mod.rs

@@ -2,7 +2,7 @@
 
 #![allow(dead_code)] // each test file uses a different part of this module
 
-use proto::{
+use bxcore::{
     ApprovalList, CallId, DataClass, Envelope, ErrorCode, Message, PROTOCOL_VERSION,
     PendingApproval, SessionId, Timestamp, TurnDone, TurnEvent, Usage, WireError, read_frame,
     write_frame,
@@ -128,7 +128,7 @@ pub fn pending(approval: u64, tool: &str, arguments: &str) -> PendingApproval {
 
 /// A `brokerd` with these approvals pending. `approve` is answered with `outcome`, `refuse` with
 /// `ok`; both answer `no_such_approval` for an id that is not in the list.
-pub fn brokerd_with(items: Vec<PendingApproval>, outcome: proto::DecisionRecord) -> FakeBrokerd {
+pub fn brokerd_with(items: Vec<PendingApproval>, outcome: bxcore::DecisionRecord) -> FakeBrokerd {
     fake_brokerd(move |msg| {
         let known = |id: u64| items.iter().any(|item| item.approval == id);
         match msg {
@@ -136,11 +136,11 @@ pub fn brokerd_with(items: Vec<PendingApproval>, outcome: proto::DecisionRecord)
                 items: items.clone(),
             }),
             Message::Approve(a) if known(a.approval) => {
-                Message::ApproveResult(proto::ApproveResult {
+                Message::ApproveResult(bxcore::ApproveResult {
                     outcome: outcome.clone(),
                 })
             }
-            Message::Refuse(r) if known(r.approval) => Message::Ok(proto::Empty {}),
+            Message::Refuse(r) if known(r.approval) => Message::Ok(bxcore::Empty {}),
             Message::Approve(_) | Message::Refuse(_) => {
                 wire_error(ErrorCode::NoSuchApproval, "no such approval")
             }