feat: add campaign objectives and KPIs support

[Copilot]

Campaigns can now define measurable objectives with KPIs to track progress toward outcomes. This enables AI agents to optimize for specific metrics rather than just completing tasks.

Changes

• Campaign Spec: Added Objective (string) and KPIs (array of KPI objects) fields with validation ensuring they're used together
• KPI Structure: Each KPI includes name, priority (primary/supporting), baseline/target values, time window, direction, and optional unit
• Orchestrator: Renders objectives and KPIs in workflow markdown and agent instructions to guide decision-making
• Validation: Enforces single primary KPI when multiple KPIs defined; validates required fields and relationships
• Push Memory: Campaign mode now validates cursor and metrics snapshot structure, ensuring campaign_id consistency

Example campaign spec with objectives:

---
id: incident-response
name: Incident Response Campaign
objective: Reduce mean time to resolution for P0 incidents
kpis:
  - name: MTTR
    priority: primary
    baseline: 4.5
    target: 2.0
    time-window-days: 30
    unit: hours
    direction: decrease
  - name: Incident recurrence rate
    priority: supporting
    baseline: 0.15
    target: 0.05
    time-window-days: 90
    unit: percent
    direction: decrease
---

The orchestrator now includes objective and KPIs in agent context, enabling measurable optimization of campaign outcomes.

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