[Integration]: Limit observer preset — rate and token budget circuit breaker

[rosspeili]

Area

observers

Kind

enhancement

Description

ROADMAP.md lists Limit observer preset (rate/budget circuit breaker). Monitor (#31) and Break (#34) shipped; Limit completes the enforce-plane trio in field-services.md.

Ship:

• aura/observers/presets/limit.py — subscribe to tool.call / token-bearing events; track rolling counts vs config (max_tokens_per_window, max_calls_per_minute, etc.)
• Emit observer.note before threshold; observer.alert at breach (alert-only by default — host pause remains playbook #47)
• Example snippet in examples/07-observer-presets or example 10 cross-link
• Tests: synthetic spine feed triggers alert; no false positive on single call
• Wire optional attach via spectrum.services: [limit] when #74 draft lands

Repro or pipeline spec (optional)

observers:
  - preset: limit
    id: budget-guard
    config:
      max_tokens_per_step: 8000
      max_tool_calls_per_minute: 30

Stress reference: scripts/aura_host_stress_sim.py tailored observers scenario.