feat: add Augment Code platform support

[ucguy4u]

Summary

Adds Augment Code as a supported installation platform. Augment Code discovers skills from ~/.augment/skills/ via SKILL.md files — the same format this project already uses — so no changes to skill files are needed.

Linked issue(s)

None — self-contained, low-risk installer addition following the same pattern as every other platform.

How I tested this

bash install.sh augment

→ Updating existing checkout at ~/.understand-anything/repo
Already up to date.
→ Linking skills for augment (per-skill → ~/.augment/skills)
  ✓ ~/.augment/skills/understand-chat → ...
  ✓ ~/.augment/skills/understand-dashboard → ...
  ✓ ~/.augment/skills/understand-diff → ...
  ✓ ~/.augment/skills/understand-domain → ...
  ✓ ~/.augment/skills/understand-explain → ...
  ✓ ~/.augment/skills/understand-figma → ...
  ✓ ~/.augment/skills/understand-knowledge → ...
  ✓ ~/.augment/skills/understand-onboard → ...
  ✓ ~/.augment/skills/understand → ...
→ Linking universal plugin root
✓ Installed Understand-Anything for augment
  Restart your CLI or IDE to pick up the skills.

All 9 skills symlinked correctly and discovered by Augment Code after restart.

• pnpm lint
• pnpm --filter @understand-anything/core test
• pnpm test (497 passed, 12 skipped — including platform-table-consistency tests that enforce install.sh, install.ps1, and README stay in sync)
• Manual smoke test: bash install.sh augment — all skills installed and picked up by Augment Code

Versioning

• N/A — installer/docs-only change