Add .github/ISSUE_TEMPLATE/agent-work-item.md issue template following leather convention

[TGPSKI]

Context

• SKILL.md (generate-directed-contexts skill — primary instruction file for the generate-directed-contexts persona in this repo)
• Leather replicates this pattern in .github/ISSUE_TEMPLATE/agent-work-item.md which is loaded by opencode when a task is scoped to a specific domain

Work

• Create .github/ISSUE_TEMPLATE/agent-work-item.md with the minimal template:

  ---
  name: Agent work item
  about: Minimal issue body for agent-consumable units of work
  title: ""
  labels: agent-work
  ---
  
  ## Context
  - SKILL.md
  
  ## Work
  - [ ] 

  This mirrors the leather convention exactly, just swapping AGENTS.md → SKILL.md so issues opened against directed-contexts default to referencing the skill as the primary instruction surface for the agent.