feat(consciousness): async tool execution (BRO-459)

[broomva]

Summary

• Move agent tick loop from blocking the consciousness event loop to a spawned tokio task, keeping the actor responsive during LLM calls + tool execution
• Add CycleCompleted, ToolResult, ToolFailed event variants and WaitingForTools mode for future per-tool async
• Use WeakSender for the self-referencing channel to preserve channel-close shutdown semantics
• Sequential queue drain via CycleCompleted -> drain_queue_after_run chain (one cycle at a time)

Changes

• crates/arcand/src/consciousness.rs: New spawn_agent_cycle + run_agent_cycle_inner methods, updated event loop and handle_user_message
• crates/arcand/tests/consciousness_test.rs: 2 new integration tests (non_blocking_cycle_completes, cycle_completed_drains_queue)

Test plan

• cargo fmt --check passes
• cargo clippy -p arcand passes (zero warnings)
• cargo test -p arcand --test consciousness_test — 9/9 tests pass (7 existing + 2 new)
• cargo test --workspace — full workspace passes (zero failures)
• Manual verification with real LLM provider (send concurrent messages, verify non-blocking behavior)

🤖 Generated with Claude Code

[linear]

BRO-459 Phase 5: Async tool execution — tools as background tasks

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 834e2e16-7918-41b2-94a0-95dfad55894d

📥 Commits

Reviewing files that changed from the base of the PR and between 2e54e27 and e847063.

📒 Files selected for processing (2)

• crates/arcand/src/consciousness.rs
• crates/arcand/tests/consciousness_test.rs

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/bro-459-async-tool-execution

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