feat: add projects create command and --sort-order flag for issues

[chadrwalters]

Summary

This PR adds two features to linearis:

1. projects create command - Create Linear projects from the CLI

   • Required --team flag (accepts team key, name, or UUID; comma-separated for multiple)
   • Optional flags: --description, --color, --icon, --lead, --target-date, --start-date, --state
   • Input validation for dates (YYYY-MM-DD) and state values

2. --sort-order flag for issues create and issues update

   • Control issue position relative to other issues (lower values = higher in list)
   • Input validation for numeric values

Changes

• Added GraphQLProjectsService with createProject() method
• Added ProjectCreateArgs type definition
• Added PROJECT_FRAGMENT and CREATE_PROJECT_MUTATION GraphQL queries
• Extended LinearProject type to include startDate field
• Added 10 unit tests for the new functionality
• Updated CHANGELOG

Testing

# Test projects create help
linearis projects create --help

# Test validation
linearis projects create "Test" --team ENG --start-date "invalid"
# Error: Invalid --start-date "invalid". Must be YYYY-MM-DD format.

linearis issues create "Test" --team ENG --sort-order invalid
# Error: Invalid --sort-order value "invalid": must be a number

# All unit tests pass
npm test

Checklist

• Tests pass (npm test)
• Follows Conventional Commits
• Updated CHANGELOG

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🤖 Generated with Claude Code

[mwolson]

If a view is using the "sort by priority" option, it would also be neat to support --priority-sort-order for mutating the prioritySortOrder field.