feat(tui): expose stream chunk timeout config

[Hmbown]

Summary

• harvest the focused stream idle-timeout config work from feat(tui): expose stream chunk timeout config #2507 for slow local/OpenAI-compatible servers reported in Stream timeout #2365
• add [tui].stream_chunk_timeout_secs plus /config stream_chunk_timeout_secs, including live session updates, --save, 0 -> default handling, and a Network row in the config view
• thread the resolved timeout through EngineConfig and DeepSeekClient so both the outer turn-loop timeout and inner SSE byte-stream timeout use the same value, while preserving DEEPSEEK_STREAM_IDLE_TIMEOUT_SECS as a fallback

Credit

Harvested from PR #2507 by @cyq1017.
Reported by @mserrano11 in #2365.

Verification

• cargo test -p codewhale-tui --bin codewhale-tui --locked stream_chunk_timeout -- --nocapture
• cargo test -p codewhale-tui --bin codewhale-tui --locked client_stream_idle_timeout_uses_tui_config -- --nocapture
• cargo test -p codewhale-tui --bin codewhale-tui --locked config_view -- --nocapture
• cargo fmt --all -- --check
• git diff --check
• ./scripts/release/check-versions.sh
• python3 scripts/check-coauthor-trailers.py --range codex/v0.9.0-stewardship..HEAD --check-authors

[greptile-apps]

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[gemini-code-assist]

Code Review

This pull request introduces the [tui].stream_chunk_timeout_secs configuration option and a corresponding /config stream_chunk_timeout_secs command, allowing users to customize the SSE stream idle timeout. It maintains backward compatibility with the legacy DEEPSEEK_STREAM_IDLE_TIMEOUT_SECS environment variable and adds persistence support, UI updates, and documentation. Feedback highlights two key issues: first, live updates to the timeout via /config are not propagated to the active DeepSeekClient instance, rendering session-only updates ineffective; second, the setting is incorrectly marked as ConfigScope::Session instead of ConfigScope::Saved in the TUI view, which prevents users from persisting it through the TUI configuration editor.

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[gemini-code-assist]

Live Update Not Propagated to DeepSeekClient

When the /config stream_chunk_timeout_secs <value> command is executed, it sends Op::SetStreamChunkTimeout to the engine, which correctly updates self.config.stream_chunk_timeout. However, the active DeepSeekClient instance (which actually performs the network requests and handles the SSE stream) is not updated with this new timeout.

Because DeepSeekClient is constructed with a fixed stream_idle_timeout at startup (or whenever it is instantiated using the global Config), any live session-only changes to the timeout will not affect the inner SSE byte-stream idle timeout (used in crates/tui/src/client/chat.rs).

For example, if a user increases the timeout to 600 seconds to accommodate a slow local server, the inner SSE stream will still timeout and fail after the default 300 seconds, rendering the live session update ineffective.

Suggested Fix

Consider one of the following approaches:

1. Pass the timeout dynamically from the engine's self.config.stream_chunk_timeout as an argument to the streaming/chat request methods on DeepSeekClient instead of storing it as a fixed field in the client.
2. Introduce interior mutability (e.g., Arc<std::sync::atomic::AtomicU64> or a thread-safe setter) to DeepSeekClient so that its timeout can be updated dynamically when Op::SetStreamChunkTimeout is processed.

[gemini-code-assist]

Inconsistent Config Scope in TUI View

The stream_chunk_timeout_secs setting is defined here with scope: ConfigScope::Session. However, this is a standard persistent configuration option in config.toml (under [tui]), and the /config command fully supports persisting it to disk via --save (using persist_tui_integer_key).

Marking it as ConfigScope::Session in the TUI config view prevents it from being saved to the persistent configuration file when the user saves their settings from the TUI config editor interface. It should be changed to ConfigScope::Saved to allow full persistence support from the TUI.

                section: ConfigSection::Network,
                key: "stream_chunk_timeout_secs".to_string(),
                value: app.stream_chunk_timeout_secs.to_string(),
                editable: true,
                scope: ConfigScope::Saved,
            },