v0.5.0

Added

• skillgate scaffold — generates .skillgate/evidence/ directory with stack-specific
  evidence file templates (generic, react, ts-lib, python). The agent must write
  these files (test output, lint report, self-review) before crossing the finish line.
  --template selects the stack; --update-agents appends workflow instructions to
  AGENTS.md / CLAUDE.md.
• skillgate diff-instructions — shows line-level diff between drifted instruction
  files (CLAUDE.md, AGENTS.md, …) rather than just a similarity percentage. Makes drift
  actionable, not just visible.
• skillgate canonical <file> — sets which instruction file is the single source of
  truth by writing .skillgate/canonical-instructions.txt.
• skillgate init now includes the instruction-sync gate and a commented-out
  evidence gate example by default — drift detection and evidence workflow are ready
  from the first init.
• lineDiff() and formatDiff() in drift.ts — reusable diff utilities for showing
  line-level changes between instruction files.

Changed

• init template modernized: instruction-sync is an active gate; evidence appears
  as a commented-out example ready to uncomment.