fix: increase DEFAULT_CHUNK_TIMEOUT from 2min to 5min (#844)

The 120s SSE chunk timeout was too aggressive for slow LLM providers,
causing spurious "SSE read timed out" aborts during long-running
multi-tool sessions. Increase to 300s to reduce false positives.

Co-authored-by: saravmajestic <saravmajestic@altimate.ai>

Author: altimate-harness-bot[bot]

packages/opencode/src/provider/provider.ts

@@ -54,7 +54,7 @@ import { VALID_ACCOUNT_RE } from "../altimate/plugin/snowflake"
 import { isValidDatabricksHost } from "../altimate/plugin/databricks"
 // altimate_change end
 
-const DEFAULT_CHUNK_TIMEOUT = 120_000
+const DEFAULT_CHUNK_TIMEOUT = 300_000
 
 export namespace Provider {
   const log = Log.create({ service: "provider" })