Select any of the transcript, and take a queued message back

Two things a reader could not do to what is on screen.

**Selection.** Nothing in the transcript was selectable at all, so a
command, a path or an error message could be read and not copied. One
`SelectionContainer` around the whole list rather than one per row: a
transcript is one body of text to a reader, and a selection has to be able
to run from a reply into the tool output under it. Per row it also could
not, and whatever was drawn without a container would have been silently
unselectable -- a state nothing on screen reports. Rows keep their tap
handlers; checked on the emulator that expanding a tool call, scrolling and
flinging are all unaffected, since a selection is a long press.

**Taking a message back.** A message sent into a running turn sits as a
bubble waiting to be read, and there was no way to change your mind: it is
tappable now, and the server answers `POST /sessions/{id}/unqueue`.

The answer has three states, and the middle one is the point. Claude's
driver writes a steer into the CLI's stdin the instant it arrives -- that
is what makes it reach the model at the next tool boundary rather than at
the end of the turn, and it was measured -- so the line is already gone and
`AlreadySent` is the only honest answer it can give. Holding the write
until a boundary would make the drop real and cost a steer one model call,
which is the latency the immediate write exists to remove; rejected on that
trade, with the reasoning in PLAN.md. The refusal is drawn on the bubble
that was pressed rather than in the error row under the header, a screen
away from it.

Where a driver really does hold its queue -- echo today -- the message goes
for good, and it goes as an `Event::MessageDropped` rather than as a return
value: every device watching the session loses the bubble, and a phone that
reconnects and replays the `messageQueued` does not put back one that was
cancelled with nothing left to resolve it.

AGENTS.md

@@ -245,6 +245,20 @@ first if a remote spawn ever mangles an argument.
   on the same transcript. What that costs is that the rows below slide up
   under the reader's finger, so a row that has just moved ignores taps for
   half a second (`SETTLE_MS`).
+- **All transcript text is selectable, from one `SelectionContainer` around
+  the whole list** (`TranscriptList.kt`). Not per row: a transcript is one
+  body of text to a reader, so a selection has to be able to run from a
+  reply into the tool output under it -- and a container per row leaves
+  whatever was drawn without one silently unselectable, which nothing on
+  screen reports. Rows keep their tap handlers; selection is a long press.
+- **A queued message can be tapped to take it back**, which is
+  `POST /sessions/{id}/unqueue` and a `messageDropped` event -- see PLAN.md's
+  "Taking a queued message back". On a **Claude** session it always refuses,
+  and that is correct rather than broken: the driver writes a steer into the
+  CLI the moment it arrives, so what the bubble is waiting for is the CLI
+  *reading* it, not this server sending it. The refusal is drawn on the
+  bubble. The echo driver really does hold its queue, so that is the rig for
+  the case where the drop succeeds.
 - **Deleting a session offers to take the machine's own transcript with
   it.** `DELETE /sessions/{id}?deleteForeign=true`, behind a switch in the
   confirmation, and only where the driver keeps a record of its own