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/utils/resolve-output.ts

@@ -0,0 +1,39 @@
+import os from "os"
+import path from "path"
+import type { TargetScope } from "../targets"
+
+export function resolveTargetOutputRoot(options: {
+  targetName: string
+  outputRoot: string
+  codexHome: string
+  piHome: string
+  hasExplicitOutput: boolean
+  scope?: TargetScope
+}): string {
+  const { targetName, outputRoot, codexHome, piHome, hasExplicitOutput, scope } = options
+  if (targetName === "codex") return codexHome
+  if (targetName === "pi") return piHome
+  if (targetName === "droid") return path.join(os.homedir(), ".factory")
+  if (targetName === "cursor") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".cursor")
+  }
+  if (targetName === "gemini") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".gemini")
+  }
+  if (targetName === "copilot") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".github")
+  }
+  if (targetName === "kiro") {
+    const base = hasExplicitOutput ? outputRoot : process.cwd()
+    return path.join(base, ".kiro")
+  }
+  if (targetName === "windsurf") {
+    if (hasExplicitOutput) return outputRoot
+    if (scope === "global") return path.join(os.homedir(), ".codeium", "windsurf")
+    return path.join(process.cwd(), ".windsurf")
+  }
+  return outputRoot
+}