Index the tpt-backend plans w/ a README

Landing page for `ai/tpt-backends/`: points at the contract spec
as required first reading, tables the 3 plans against their
issues/deps/size, and states the landing order + why.

Deats,
- TIPC first as the cheap proof the table-registration story
  generalizes to a genuinely new proto (stdlib-only, and
  `trio`'s sock wrappers are family-agnostic).
- `wg` layer-A next since it's deployable-today doc/example work.
- QUIC last, gated on its own prep PR.
- notes that plans 01 and 02 both want the same
  `Address.rebind_from_sockname` gate, so whichever lands first
  ships it.

(this patch was generated in some part by `claude-code` using `claude-opus-5` (`anthropic`))

ai/tpt-backends/README.md

@@ -0,0 +1,54 @@
+# next-gen `tractor.ipc` transport backend plans
+
+Implementation specs for three prospective `.ipc` transport
+backends, written so each can be worked independently (by a
+different model/provider) without design or lib-selection drift.
+
+**Read [`00_shared_backend_contract.md`](./00_shared_backend_contract.md)
+first** — it is the normative description of what a `tractor`
+transport backend *is* as of `main@83b34884` (the backend
+duck-type, the 10-item registration checklist, the test-harness
+plumbing, the code-style rules). The three plans assume it and
+document only their own deltas.
+
+| plan | issue | dep | size | lands |
+| --- | --- | --- | --- | --- |
+| [01 — TIPC](./01_tipc_backend.md) | [#378] | **none** (stdlib) | small | first |
+| [02 — QUIC/`iroh`](./02_quic_iroh_backend.md) | [#353] | `iroh` (uniffi FFI) | large | needs a prep PR |
+| [03 — `wg` bindspace](./03_wg_tunnel_bindspace.md) | [#482], [#443] | `pyroute2` | medium, 3 layers | layer A now |
+
+Headline conclusions:
+
+- **TIPC is the cheap win.** Verified: `trio.SocketStream` and
+  `trio.SocketListener` are address-family agnostic (only
+  `SOCK_STREAM` + a trio socket), and CPython ships `AF_TIPC` +
+  23 `TIPC_*` constants. So the backend is ~one module of
+  contract boilerplate, zero new deps, and it buys
+  *kernel-native* service discovery: `bind()` publishes,
+  `connect()`-by-name resolves — no registrar in the loop.
+  (`modprobe tipc` is required; hard-gate everything.)
+- **QUIC's cost is entirely in two adapters**, not in QUIC. The
+  `iroh` python bindings are `uniffi`-generated asyncio, but the
+  asyncio dependency is confined to *one* future-poll callback —
+  a ~40-line `trio` bridge (`TrioToken.run_sync_soon`) replaces
+  it. The second cost is that an iroh listener isn't a socket,
+  which needs a small, independently-reviewable prep PR to
+  `_server.py`/`_types.py`.
+- **WireGuard is not a transport.** It's an iface-layer tunnel,
+  so it belongs as a *nested bindspace* (`TunnelledAddress` +
+  `open_bindspace()` `@acm`s) wrapping whatever L4 tpt is in
+  use — which is also what finally implements the long-spec'd
+  `Address.namespace`, and what generalizes to
+  `veth`/`vxlan`/`gre`.
+
+Ordering rationale: plan 01 first as the cheap proof the
+table-registration story generalizes to a genuinely new proto;
+plan 03 layer A is already deployable-today doc/example work;
+plan 02 last (and gated on its prep PR). Plans 01 and 02 both
+want the same `Address.rebind_from_sockname` gate — whichever
+lands first ships it.
+
+[#378]: https://github.com/goodboy/tractor/issues/378
+[#353]: https://github.com/goodboy/tractor/issues/353
+[#482]: https://github.com/goodboy/tractor/issues/482
+[#443]: https://github.com/goodboy/tractor/issues/443