feat: consumer-session — TunnelSession (open/adopt, data planes, teardown)

- TunnelSession (src/consumer.rs): open (ChannelClient::open_channel)
  + adopt (ChannelManager::adopt_channel) construction, substrate-
  shaped data planes (raw halves for stream; ADR-003 codec + pending
  frame queue for UDP), pump_against (session-owned pump_bidi handle),
  and teardown ownership per ADR-005: close (abort + ungraceful reap),
  join (await + reap + copy counts, pump-less (0,0,reaped)), Drop
  (abort + sync reap, never leaks). No Clone (compile_fail doc-test).
- open_reverse_channel on the CallConnection (the reverse path's
  two-step: call then adopt — the POC's honest shape).
- Error surfaces (src/error.rs): TunnelOpenError (typed ADR-049 §4
  surface via open_ref/establishment_reason), TunnelIoError (wrong-
  substrate, TruncatedDatagram fail-loud, ChannelTaken), ReverseOpenError.
- Tests: tests/consumer_session.rs (12) over two harness topologies —
  forward (wire_forward/ForwardTopology: consumer connect-side pure
  client, producer serving via adapter) and reverse (the POC shape);
  teardown matrix, W4 half-close, out-of-band close + self-reap (W3),
  F-2 empty datagram, AdoptFailed-on-collision (bogus-id adopt parks
  by design — documented), concurrent sessions. Harness: all_substrate_dial.
- Adopt takes substrate (task-note deviation: the data plane shape
  rode the open call; cannot be inferred from the ID).

Verified: cargo test green (38), clippy -D warnings (native + wasm32),
fmt clean, cargo check --target wasm32-unknown-unknown passes.

Cargo.toml

@@ -28,4 +28,5 @@ tracing = "0.1"
 thiserror = "2"
 
 [dev-dependencies]
-tokio = { version = "1", features = ["full", "test-util", "macros"] }
+tokio = { version = "1", features = ["full", "test-util", "macros"] }
+tracing-subscriber = { version = "0.3.23", features = ["env-filter"] }