feat(windsurf): add workflow support for Windsurf

[itgcl]

Closes #136

Summary

Add workflow support for Windsurf.

Changes

• add --windsurf init option
• add Windsurf platform registration and configurator
• generate workflow files under .windsurf/workflows/
• add Windsurf template extraction and Trellis runtime path/platform adapter support
• add test coverage for init, configurator, template loading, and regression cases
• update README / README_CN supported platform docs

Scope

Included:

• Windsurf workflows

Not included:

• Windsurf hooks
• Windsurf rules

Design Notes

• workflow filenames use trellis-*.md
• trigger naming follows /trellis-*
• Windsurf templates are implemented independently and do not reference other editor templates at runtime
• the parallel workflow is excluded for Windsurf because the required CLI multi-agent flow is not supported

Verification

cd packages/cli
pnpm lint
pnpm typecheck
pnpm test test/templates/windsurf.test.ts test/configurators/platforms.test.ts test/commands/init.integration.test.ts test/configurators/index.test.ts test/templates/extract.test.ts
pnpm test test/regression.test.ts -t windsurf
pnpm build