v0.4.0: HasPendingTx accessor (mirror of fpc-binkp 0.4.0)

Add public read-only TComSession.HasPendingTx returning True iff
there are outbound bytes already queued in the send stream that
haven't been pushed to the socket yet.  Mirror of the same
accessor added to fpc-binkp's TBPSession in 0.4.0.  Lets driver
loops pass it as the WantWrite flag in Transport.WaitReady;
primarily a perf improvement for high-volume sends (avoids
per-frame idle wait).

Recommended pattern:

  while Session.NextStep do
    Transport.WaitReady(True, Session.HasPendingTx, 50);

Wire protocol unchanged.  Consumers pinned to 0.3.0 can upgrade
in place; HasPendingTx is purely additive and callers that
don't use it keep the old behaviour.
CM_MIN_COMPATIBLE_VERSION stays at 0.1.0.

CHANGELOG.md

@@ -10,6 +10,31 @@ Semver intent:
 - **minor** — additive features, new hooks, new capability flags
 - **patch** — bug fixes, security hardening, internal perf
 
+## 0.4.0 — 2026-04-25
+
+### Added
+
+- **`TComSession.HasPendingTx: Boolean`** — public read-only
+  accessor.  True iff there are outbound bytes already
+  queued in the send stream that haven't been pushed to
+  the socket yet.  Mirror of the same accessor added to
+  fpc-binkp's `TBPSession` in 0.4.0.  Lets driver loops
+  pass it as the `WantWrite` flag in
+  `Transport.WaitReady`; primarily a perf improvement for
+  high-volume sends (avoids per-frame idle wait).
+- Recommended driver loop pattern:
+  ```pascal
+  while Session.NextStep do
+    Transport.WaitReady(True, Session.HasPendingTx, 50);
+  ```
+
+### Not changed
+
+- Wire protocol unchanged; consumers pinned to 0.3.0 can
+  upgrade in place.  `HasPendingTx` is purely additive --
+  callers that don't use it keep the old behaviour.
+- `CM_MIN_COMPATIBLE_VERSION` stays at `0.1.0`.
+
 ## 0.3.0 — 2026-04-24
 
 ### Changed

src/cm.driver.pas

@@ -181,6 +181,16 @@ type
     function Phase: TCometPhase;
     function Result_: TCometSessionResult;
 
+    { True iff there are outbound bytes already queued in the
+      send stream that haven't been pushed to the socket yet.
+      Driver loops use this to choose whether WaitReady should
+      also wait for socket WRITE-readiness -- when True,
+      select() returns the moment the kernel send buffer can
+      take more bytes, so high-volume transfers don't pay a
+      50 ms idle wait per frame.  Mirror of the same accessor
+      on fpc-binkp's TBPSession. }
+    function HasPendingTx: Boolean;
+
     { ---- Hooks for cm.xfer ---- }
     { Queue a complete frame onto the outbound stream.  Bytes
       drain to the transport on the next NextStep / Pump. }
@@ -1288,6 +1298,12 @@ begin
   Result := FResult;
 end;
 
+function TComSession.HasPendingTx: Boolean;
+begin
+  Result := (FSendStream <> nil) and
+            ((FSendStream.Size - FSendPos) > 0);
+end;
+
 procedure TComSession.EmitFrame(PktType, Seq: Byte; const Buf;
   Len: SizeInt);
 var

src/cm.version.pas

@@ -21,9 +21,9 @@ interface
 
 const
   CM_VERSION_MAJOR = 0;
-  CM_VERSION_MINOR = 3;
+  CM_VERSION_MINOR = 4;
   CM_VERSION_PATCH = 0;
-  CM_VERSION       = '0.3.0';
+  CM_VERSION       = '0.4.0';
 
   { Oldest version a consumer pinned to CM_VERSION is
     guaranteed to remain ABI/API-compatible with.  Bumped