Replace Malformed(String) with a no_std-clean set: Malformed(&static str)
for the static decode diagnostics, BadSizeClass { got, max } for the two
bloom size-class checks, and typed sources BadCoord(CoordError) /
BadBloom(BloomError) for the coordinate and bloom construction failures. Add a
dedicated CoordError so proto/coord no longer depends upward on stp TreeError,
resolving the temporary inversion from the coordinate relocation. Drop the
thiserror derive from the four proto error types (Error, TreeError, BloomError,
CoordError) in favor of hand-rolled core::fmt::Display and core::error::Error
impls. thiserror remains in use elsewhere in the crate. Wire decode decisions
are unchanged; only the error type and its diagnostic text change.
Migrate the FSP end-to-end session subsystem into src/proto/fsp/ following the
established sans-IO shape, and retire the src/protocol grab-bag now that FSP was
its last occupant.
Relocate the FSP session wire (node/session_wire.rs plus the FSP message types
from protocol/session.rs) into proto/fsp/wire.rs. Hoist the pure decision logic
into proto/fsp/core.rs over plain-data SessionSnapshots returning an ordered
FspAction list the shell drives: session-rekey policy, msg3-resend
classification, post-decrypt epoch reaction, setup/dual-init tie-break,
coords/path-MTU emit-policy, bounded pending-queue, and IPv6 ECN. The
crypto-owning SessionEntry stays shell-side in node/session.rs (matching the FMP
ActivePeer pattern); proto/fsp is wire + core + limits only, with no proto->noise
dependency and no crypto.
Move the coords helpers to proto/stp/ (they serialize TreeCoordinate), and split
SessionMessageType: the encrypted-inner 0x10-0x1F variants stay in proto/fsp/wire.rs
while the 0x20-0x2F routing signals become a new RoutingSignalType in
proto/routing/wire.rs. Migrate the session-MMP shell adapter, which continues to
drive proto/mmp/.
Retire src/protocol: LinkMessageType and SessionDatagram move to a new shared
proto/link.rs, ProtocolError becomes proto::Error (relocated verbatim), the
deprecated MessageType alias and the unimported PROTOCOL_VERSION are dropped, and
src/protocol/ is deleted along with its lib.rs module declaration.
Behavior-neutral: wire bytes unchanged, oracle tests pass unedited except
mod-path relocation; adds rekey/epoch characterization tests and pure
poll/emit-policy core tests.
Johnathan Corgan