CABI: refactor/simplify stream/future logic; fix delivery of DROPPED/CANCELLED

design/mvp/Concurrency.md

@@ -600,8 +600,8 @@ and writable ends of streams and futures can then be
 progress signals *completion* of a read or write (i.e., the bytes have already
 been copied into the buffer). Additionally, *readiness* (to perform a read or
 write in the future) can be queried and signalled by performing a `0`-length
-read or write (see the [Stream State] section in the Canonical ABI explainer
-for details).
+read or write (see the [Stream and Future State] section in the Canonical ABI
+explainer for details).
 
 As a temporary limitation, if a `read` and `write` for a single stream or
 future occur from within the same component and the element type is a
@@ -619,8 +619,8 @@ without requiring an explicit `future` return type. Thus, a function like
 which point the caller receives the readable end of a `future` that, when
 successfully read, conveys the completion of a second event.
 
-The [Stream State] and [Future State] sections describe the runtime state
-maintained for streams and futures by the Canonical ABI.
+The [Stream and Future State] section describes the runtime state maintained for
+streams and futures by the Canonical ABI.
 
 ### Stream Readiness
 
@@ -1574,8 +1574,7 @@ the concurrency story:
 [`ComponentInstance`]: CanonicalABI.md#component-instances
 [`Thread`]: CanonicalABI.md#threads
 [`Task`]: CanonicalABI.md#tasks
-[Stream State]: CanonicalABI.md#stream-state
-[Future State]: CanonicalABI.md#future-state
+[Stream and Future State]: CanonicalABI.md#stream-and-future-state
 
 [Binary Format]: Binary.md
 [WIT]: WIT.md

design/mvp/Explainer.md

@@ -2005,7 +2005,7 @@ the buffer parameter is ignored.
 If the return value is a `stream-result`, then the `progress` field indicates how
 many `T` elements were read or written from the given buffer before the
 `copy-result` was reached. For example, a return value of `{progress: 4,
-result: dropped}` from a `stream<u32>.read` means that 32 bytes were copied
+result: dropped}` from a `stream<u32>.read` means that 16 bytes were copied
 into the given buffer before the writer end dropped the stream. The `cancelled`
 case can only arise as the result of a call to `stream.cancel-{read,write}`.
 
@@ -3419,8 +3419,8 @@ For some use-case-focused, worked examples, see:
 [`canon_waitable_set_drop`]: CanonicalABI.md#-canon-waitable-setdrop
 [`canon_waitable_join`]: CanonicalABI.md#-canon-waitablejoin
 [`canon_stream_new`]: CanonicalABI.md#-canon-streamfuturenew
-[`canon_stream_read`]: CanonicalABI.md#-canon-streamreadwrite
-[`canon_future_read`]: CanonicalABI.md#-canon-futurereadwrite
+[`canon_stream_read`]: CanonicalABI.md#-canon-streamfuturereadwrite
+[`canon_future_read`]: CanonicalABI.md#-canon-streamfuturereadwrite
 [`canon_stream_cancel_read`]: CanonicalABI.md#-canon-streamfuturecancel-readwrite
 [`canon_stream_drop_readable`]: CanonicalABI.md#-canon-streamfuturedrop-readablewritable
 [`canon_subtask_cancel`]: CanonicalABI.md#-canon-subtaskcancel