OSS launch polish: fix hook paths, add OSS files, update README

- Fix slashes in agent identity causing invalid hook file paths (gt-vqhc)
- Add Prerequisites section to README (gt-vzic)
- Create CONTRIBUTING.md, CODE_OF_CONDUCT.md, SECURITY.md (gt-xbfw)
- Update Install section for future package managers (gt-7wcf)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/wisp/io.go

@@ -100,11 +100,7 @@ func ListHooks(root string) ([]string, error) {
 
 	var agents []string
 	for _, e := range entries {
-		name := e.Name()
-		if len(name) > len(HookPrefix)+len(HookSuffix) &&
-			name[:len(HookPrefix)] == HookPrefix &&
-			name[len(name)-len(HookSuffix):] == HookSuffix {
-			agent := name[len(HookPrefix) : len(name)-len(HookSuffix)]
+		if agent := AgentFromHookFilename(e.Name()); agent != "" {
 			agents = append(agents, agent)
 		}
 	}