fix(zsh): streaming placeholder not updated when async is enabled (#7443)

* fix: streaming placeholder not updated when async is enabled

When both async and streaming are configured on ZSH, the init command
becomes 'precmd() { source <script> }', which re-sources the script on
every prompt cycle. This unconditionally reset _omp_stream_fd=-1, causing
_omp_cleanup_stream to skip closing the previous cycle's stream fd.

The stale stream's EOF handler would later call _omp_cleanup_stream using
the global _omp_stream_fd (now pointing to the new stream's fd) and kill
the new stream before it could send any updates. The placeholder never
got replaced.

Three fixes:

1. init.go: Skip async sourcing when streaming is also active. Streaming
   provides its own async update mechanism; re-sourcing on every precmd is
   not needed and conflicts with the streaming fd lifecycle.

2. omp.zsh (_omp_stream_fd init): Use \ so a
   re-source does not clobber an in-flight stream fd.

3. omp.zsh (_omp_async_handler): On EOF, close only the specific fd that
   triggered the handler instead of calling _omp_cleanup_stream. This
   prevents any stale handler from closing the current stream's fd even if
   the global variable has diverged.

Fixes #7313

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(zsh): streaming placeholder not updated when async is enabled

When both async and streaming are configured in ZSH, the omp.zsh script
is re-sourced before every prompt cycle via the async init mechanism
(precmd() { source <script> }).  Top-level variable assignments in the
re-sourced script run unconditionally, so _omp_stream_fd was reset to -1
on every prompt cycle even while a live stream was in flight.

This caused two problems:
1. _omp_cleanup_stream skipped cleanup (fd -1 < 0) before starting the
   new stream, leaking the old fd and its ZLE handler.
2. The stale EOF handler later fired, saw _omp_stream_fd pointing at the
   NEW stream, and closed it  so the placeholder was never replaced.

Fix 1: use _omp_stream_fd=\ (ZSH := modifier) so
the fd value survives a re-source, initialising to -1 only when the
variable is genuinely unset (first source at shell startup).

Fix 2: in _omp_async_handler, guard the EOF cleanup with
[[ \ -eq \ ]] so a stale handler from a previous
prompt cycle can never close the current stream's fd.

Reverts the init.go change from the previous commit  changing the
async sourcing mechanism is unnecessary and caused a regression (exit
code 127) when streaming was enabled.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* fix(zsh): correct misleading comment on stream fd initialization

The comment referenced := (ZSH assign-if-unset) but the code uses :-
(use-default-if-unset). Update the comment to accurately describe
what the expansion does.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JanDeDobbeleer

src/shell/scripts/omp.zsh

@@ -17,7 +17,8 @@ _omp_cursor_positioning=0
 _omp_ftcs_marks=0
 
 # streaming support variables
-_omp_stream_fd=-1
+# Preserve the current fd value if the script is re-sourced mid-session; default to -1 when unset or empty.
+_omp_stream_fd=${_omp_stream_fd:--1}
 _omp_enable_streaming=0
 _omp_primary_prompt=""
 _omp_streaming_supported=""
@@ -110,8 +111,9 @@ function _omp_async_handler() {
   IFS= read -r -u $fd -d $'\0' _omp_primary_prompt
   if [[ $? -ne 0 ]]; then
     if [[ -z "$_omp_primary_prompt" ]]; then
-      # EOF — stream closed normally
-      _omp_cleanup_stream
+      # EOF — only clean up if this is still the active stream fd.
+      # A stale handler from a previous prompt cycle must not close the current stream.
+      [[ $_omp_stream_fd -eq $fd ]] && _omp_cleanup_stream
       return 0
     fi
   fi