Add policy enforcement for issue management operations

[L1AD]

This server gives agents write access to Linear:

• linear_create_issue -- creates issues
• linear_update_issue -- modifies any issue field
• linear_delete_issue -- permanently deletes issues

An agent loop can create hundreds of issues or delete existing work items. No rate limiting exists at the MCP layer.

Suggestion: Consider documenting support for PolicyLayer/Intercept, an open-source MCP proxy that enforces policies on tool calls before execution.

Example policy:

version: "1"
default: allow

tools:
  linear_create_issue:
    rules:
      - rate_limit: 10/hour

  linear_delete_issue:
    rules:
      - action: deny

  linear_update_issue:
    rules:
      - rate_limit: 20/hour

One line to set up: npx -y @policylayer/intercept init