Complete streamed agent tool events

[ishaan-berri]

Summary

• finalize any open Claude Code tool-use parts as completed before emitting session.idle
• keep the UI transcript from showing stale running tool calls when the live stream omits a tool stop event
• add an E2B stream regression test for missing content_block_stop

Live E2E proof

• started the local Rust server on 127.0.0.1:4017 with Anthropic + E2B env-backed config and local Postgres
• used the UI to create saved agent UI Fixed E2E 1780418774785
• started a session from that saved agent in the UI
• sent Run pwd... through the chat composer
• verified the visible transcript rendered assistant text UI_FIXED_AGENT_OK, reasoning text, Bash pwd tool activity marked done, and final idle state
• opened the UI inspector and verified event frames: session.status, message.updated, message.part.updated, message.part.delta, tool Bash · completed, text deltas, and session.idle

Checks

• cargo fmt --check
• cargo check --all-targets --locked
• cargo clippy --all-targets --all-features --locked -- -D warnings
• cargo test --locked
• npm --prefix src/ui run lint
• npm --prefix src/ui run build

Merge/conflict check

• git fetch origin && git rebase --autostash origin/codex/config-agent-ui-chat completed cleanly before commit/push