feat(sight): add ReactiveExporter for observe→act pipeline

[jfeng18]

What

The first piece of dynamic orchestration in ANOLISA: agentsight can now react to observed events, not just record them.

ReactiveExporter is a new GenAIExporter that inspects each LLM call event for critical signals and triggers actions:

• Critical interruption (crash / OOM / SIGKILL in error field) → spawn ws-ckpt checkpoint to save workspace state
• Token waste advisory (>50K input tokens with zero prompt caching) → log a recommendation

Why

From the north-star ("max power inference + dynamic workflow orchestration") gap analysis: agentsight scores 2/10 on "dynamic orchestration" because modules only observe — they never act. This PR is the 0→1: the first time a module's observation triggers another module's action.

Design

• Non-blocking: export() does try_send on a bounded channel (cap 32). Background thread runs ws-ckpt.
• Timeout-protected: try_wait poll loop with 10s deadline + kill. A stuck ws-ckpt never blocks the thread or Drop.
• Debounced: at most 1 checkpoint per interval (default 30s). Prevents storm cascades.
• Graceful: ws-ckpt not installed → new() returns None → not registered (zero cost).
• Default disabled: needs explicit config. Zero impact on existing deployments.

Config

{ "reactive": { "enabled": true, "debounce_secs": 30, "workspace": "/root" } }

Testing

• ✅ 8 unit tests (detection, advisory, disabled, integration: ws-ckpt spawn + timeout + debounce + Drop)
• ✅ 546 full regression
• ✅ ECS E2E: registers in trace mode, zero false positives on normal traffic
• ✅ ECS integration test: crash event → spawn → timeout → kill → debounce → Drop clean (13.2s)
• ✅ Adversarial review (7 agents): 1 confirmed finding (timeout hang) → fixed

🤖 Generated with Claude Code

[jfeng18]

E2E verification: full signal chain on live ECS

Triggered a real RetryStorm (6 identical invalid API calls → 5+ auth_error in one conversation) with the reactive exporter enabled and ws-ckpt daemon running:

--- interruption_events ---
auth_error|b59780476b41bbe7f6e4461c7199e096
retry_storm|b59780476b41bbe7f6e4461c7199e096

--- ws-ckpt snapshots ---
WORKSPACE            SNAPSHOT                         CREATED             MESSAGE
---------------------------------------------------------------------------------
/root/test-workspace auto-20260609T140312-retry_storm 2026-06-09 14:03:12 reactive: retry_storm (conv=b59780476b41bbe7f6e4461c7199e096)

--- reactive log ---
[2026-06-09T14:03:12Z INFO  agentsight::genai::reactive] [reactive] checkpoint created: auto-20260609T140312-retry_storm

Full chain verified: eBPF capture → interruption detection → RetryStorm insert → notify_interruption → background thread → ws-ckpt spawn → real btrfs snapshot created on disk.