feat(windsurf): add Windsurf as converter target with global scope support

Add `--to windsurf` target for the converter CLI with full spec compliance
per docs/specs/windsurf.md:

- Claude agents → Windsurf skills (skills/{name}/SKILL.md)
- Claude commands → Windsurf workflows (workflows/{name}.md, flat)
- Pass-through skills copy unchanged
- MCP servers → mcp_config.json (merged with existing, 0o600 permissions)
- Hooks skipped with warning, CLAUDE.md skipped

Global scope support via generic --scope flag (Windsurf as first adopter):
- --to windsurf defaults to global (~/.codeium/windsurf/)
- --scope workspace for project-level .windsurf/ output
- --output overrides scope-derived paths

Shared utilities extracted (resolveTargetOutputRoot, hasPotentialSecrets)
to eliminate duplication across CLI commands.

68 new tests (converter, writer, scope resolution).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/types/windsurf.ts

@@ -0,0 +1,34 @@
+export type WindsurfWorkflow = {
+  name: string
+  description: string
+  body: string
+}
+
+export type WindsurfGeneratedSkill = {
+  name: string
+  content: string
+}
+
+export type WindsurfSkillDir = {
+  name: string
+  sourceDir: string
+}
+
+export type WindsurfMcpServerEntry = {
+  command?: string
+  args?: string[]
+  env?: Record<string, string>
+  serverUrl?: string
+  headers?: Record<string, string>
+}
+
+export type WindsurfMcpConfig = {
+  mcpServers: Record<string, WindsurfMcpServerEntry>
+}
+
+export type WindsurfBundle = {
+  agentSkills: WindsurfGeneratedSkill[]
+  commandWorkflows: WindsurfWorkflow[]
+  skillDirs: WindsurfSkillDir[]
+  mcpConfig: WindsurfMcpConfig | null
+}