Execute implementation plan from tasks

Execute feature implementation plan with task execution and checklist verification

Large feature implementations with interdependent tasks, spec-driven contracts, and multi-stage quality gates (setup, test, build, integration, polish).

• · tasks.md (task list and execution plan)
• · plan.md (tech stack, architecture, file structure)
• · spec/ directory (language-agnostic specifications)
• · Optional checklists/ (UX, test, security)

• · Executed tasks in phase order (Setup → Tests → Core → Integration → Polish)
• · Generated/updated files per plan.md
• · Updated spec/ and CHANGELOG with new contracts
• · Checklist completion status

• · .specify/scripts/bash/check-prerequisites.sh (feature context)
• · Task runner (per language: npm, python, go, etc.)
• · git (ignore file management)

• · Feature directory initialized (.specify/)
• · tasks.md and plan.md exist
• · spec/ directory present (single source of truth)
• · Ignore files (gitignore, dockerignore, eslintignore) created

• · Checklists incomplete → asks user confirmation before proceeding
• · Ignore file patterns missing → adds critical patterns per tech stack
• · Task dependency violation → out-of-order execution fails
• · spec/ files out of sync → implementation deviates from contract

• · Prerequisite check includes feature directory and available docs
• · Checklist status validated before execution (PASS/FAIL)
• · Automatic ignore file generation per detected tech stack
• · spec/ is single source of truth (contract enforcement)
• · Phase-ordered execution (tests before core, core before integration)