fix(ci-queue-wait): treat absent branch (404) as queue-clear (#872)

Closes #872

Mos (id-11) Gate-16 merge: independent review APPROVE @23cbdaf8, author jason.woltje(id2) != approver Mos(id11), CI green wp1974.

Co-authored-by: jason.woltje <jason@diversecanvas.com>
Co-committed-by: jason.woltje <jason@diversecanvas.com>

packages/mosaic/framework/tools/git/ci-queue-wait.ps1

@@ -185,6 +185,16 @@ switch ($platform) {
             $headSha = ($branchPayload.commit.id | Out-String).Trim()
         }
         catch {
+            # A not-yet-pushed feature branch has no in-flight pipeline, so the
+            # pre-push queue guard must treat 404 as "queue clear", not crash.
+            $statusCode = $null
+            if ($_.Exception.Response) {
+                $statusCode = [int]$_.Exception.Response.StatusCode
+            }
+            if ($statusCode -eq 404) {
+                Write-Host "[ci-queue-wait] branch $Branch not yet on remote — no in-flight pipeline; queue clear."
+                exit 0
+            }
             Write-Error "Could not resolve $Branch head SHA from Gitea API."
             exit 1
         }