Spec Kit assets update from v0.0.90 to v0.1.6

[brooke-hamilton]

Summary

This PR updates the Spec Kit assets from v0.0.90 to v0.1.6.

Changes

Agent configuration files (.github/agents/)

• Updated constitution, plan, specify, and tasks agent definitions with revised instructions and support for additional AI agents (e.g., Antigravity)

Bash scripts (.specify/scripts/bash/)

• check-prerequisites.sh: Reformatted and updated prerequisite checks
• common.sh: Updated shared utility functions and path helpers
• create-new-feature.sh: Revised feature creation workflow
• setup-plan.sh: Updated plan setup logic
• update-agent-context.sh: Major refactor — added support for new agent types (Antigravity/agy), reformatted indentation, and updated agent file path handling

PowerShell scripts (.specify/scripts/powershell/)

• check-prerequisites.ps1: Updated prerequisite validation
• common.ps1: Updated shared PowerShell utilities
• create-new-feature.ps1: Revised feature creation workflow
• setup-plan.ps1: Updated plan setup logic
• update-agent-context.ps1: Updated agent context generation with new agent support

Templates (.specify/templates/)

• checklist-template.md: Minor updates to checklist structure
• constitution-template.md: New template added for agent constitutions
• plan-template.md: Updated plan template formatting
• spec-template.md: Updated spec template formatting
• tasks-template.md: Updated tasks template formatting

VS Code settings

• .vscode/settings.json: Updated workspace settings

Files changed

20 files changed, 1332 insertions(+), 1286 deletions(-)