fix(realtime): consume ChatDeltas when C++ autoparser clears Response (#9538)

The llama.cpp C++-side chat autoparser clears Reply.Message and delivers
parsed content/reasoning/tool-calls via Reply.chat_deltas. chat.go handles
this (non-SSE path uses ToolCallsFromChatDeltas/ContentFromChatDeltas/
ReasoningFromChatDeltas), but realtime.go only read pred.Response, so any
model routed through the autoparser (Qwen2.5/3 and friends) produced a
silent reply: backend emitted N tokens, the session surface saw zero.

Mirror the non-SSE chat path in realtime's triggerResponse: when deltas
carry tool calls or content, use them directly; otherwise fall back to
the existing raw-text parsing.

Assisted-by: claude-opus-4-7-1M [Claude Code]

Signed-off-by: Richard Palethorpe <io@richiejp.com>