Fix stream events

[sixlive]

Description

Fixes streaming event ordering in multi-turn tool conversations. Previously, providers emitted StreamEndEvent before tool execution completed and produced duplicate StreamStart/StreamEnd pairs across tool call turns.

Changes:

• Modified StreamState::reset() to preserve streamStarted flag across tool call turns
• Added conditional StreamEndEvent emission in all 9 provider Stream handlers (only emit when no pending tool calls)
• Added state reset before recursive streaming in Ollama handler to clear tool call state between turns

Before:

StreamStartEvent (turn 1)
StreamEndEvent (turn 1)      <- Too early
ToolResultEvent              <- After StreamEnd
StreamStartEvent (turn 2)    <- Duplicate
StreamEndEvent (turn 2)

After:

StreamStartEvent (once)
ToolCallEvent
ToolResultEvent
StreamEndEvent (once at true end)

Breaking Changes

[kinsta]

Preview deployments for prism ⚡️

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Commit: 80fde00cd0f1be2bfc33098aed863c5a5eece221

Deployment ID: 312fed28-6d58-4006-a475-c9bec2139f4f

Static site name: prism-97nz9