Swap `open_channel_from()` to yield `(chan, first)`

Deliver `(LinkedTaskChannel, Any)` instead of the prior `(first, chan)`
order from `open_channel_from()` to match the type annotation and be
consistent with `trio.open_*_channel()` style where the channel obj
comes first.

- flip `yield first, chan` -> `yield chan, first`
- update type annotation + docstring to match
- swap all unpack sites in tests and examples

(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

examples/debugging/asyncio_bp.py

@@ -59,7 +59,7 @@ async def trio_ctx(
         to_asyncio.open_channel_from(
             bp_then_error,
             # raise_after_bp=not bp_before_started,
-        ) as (first, chan),
+        ) as (chan, first),
 
         trio.open_nursery() as tn,
     ):

examples/infected_asyncio_echo_server.py

@@ -33,7 +33,7 @@ async def trio_to_aio_echo_server(
     # message.
     async with tractor.to_asyncio.open_channel_from(
         aio_echo_server,
-    ) as (first, chan):
+    ) as (chan, first):
 
         assert first == 'start'
         await ctx.started(first)

tests/test_child_manages_service_nursery.py

@@ -68,7 +68,7 @@ async def wrapper_mngr(
         else:
             async with tractor.to_asyncio.open_channel_from(
                 aio_streamer,
-            ) as (first, from_aio):
+            ) as (from_aio, first):
                 assert not first
 
                 # cache it so next task uses broadcast receiver

tests/test_infected_asyncio.py

@@ -237,7 +237,7 @@ async def trio_ctx(
                 trio.open_nursery() as tn,
                 tractor.to_asyncio.open_channel_from(
                     sleep_and_err,
-                ) as (first, chan),
+                ) as (chan, first),
             ):
 
                 assert first == 'start'
@@ -474,7 +474,7 @@ async def stream_from_aio(
                 trio_exit_early
             ))
 
-        ) as (first, chan):
+        ) as (chan, first):
 
             assert first is True
 
@@ -768,8 +768,8 @@ async def trio_to_aio_echo_server(
     async with to_asyncio.open_channel_from(
         aio_echo_server,
     ) as (
-        first,  # value from `chan.started_nowait()` above
         chan,
+        first,  # value from `chan.started_nowait()` above
     ):
         assert first == 'start'
 

tests/test_root_infect_asyncio.py

@@ -49,7 +49,7 @@ def test_infected_root_actor(
                 ),
                 to_asyncio.open_channel_from(
                     aio_echo_server,
-                ) as (first, chan),
+                ) as (chan, first),
             ):
                 assert first == 'start'
 
@@ -173,7 +173,7 @@ def test_trio_prestarted_task_bubbles(
                             sync_and_err,
                             ev=aio_ev,
                         )
-                    ) as (first, chan),
+                    ) as (chan, first),
                 ):
 
                     for i in range(5):

tractor/to_asyncio.py

@@ -1299,15 +1299,15 @@ async def open_channel_from(
     **target_kwargs,
 
 ) -> AsyncIterator[
-    tuple[Any, LinkedTaskChannel]
+    tuple[LinkedTaskChannel, Any]
 ]:
     '''
     Start an `asyncio.Task` as `target()` and open an
     inter-loop (linked) channel for streaming between
     it and the current `trio.Task`.
 
-    A pair `(Any, chan: LinkedTaskChannel)` is delivered
+    A pair `(chan: LinkedTaskChannel, Any)` is delivered
-    to the caller where the 1st element is the value
+    to the caller where the 2nd element is the value
     provided by the `asyncio.Task`'s unblocking call
     to `chan.started_nowait()`.
 
@@ -1333,8 +1333,7 @@ async def open_channel_from(
                     first = await chan.receive()
 
                     # deliver stream handle upward
-                    yield first, chan
+                    yield chan, first
-                    # ^TODO! swap these!!
             except trio.Cancelled as taskc:
                 if cs.cancel_called:
                     if isinstance(chan._trio_to_raise, AsyncioCancelled):