Improve repository presentation

[pdurlej]

Summary

• Rework the README first screen with clearer positioning, release/license/Go docs badges, a human-readable capability list, and project status near the top.
• Modernize the Go workflow to current GitHub Actions and the Go version declared in go.mod.
• Add contributing, security, PR template, and issue templates so the repo looks maintained and receives better bug/feature reports.
• Ignore local .serena agent cache directories.

Repository metadata was also updated directly on GitHub:

• description: Maintained Go SDK, CLI and MCP server for Things Cloud automation
• topics: things, things-cloud, things3, cultured-code, golang, cli, mcp, model-context-protocol, automation, task-management, openclaw, agents

Verification

• YAML parsed with Ruby YAML.load_file for workflow and issue forms
• git diff --check
• GOCACHE=/private/tmp/go-build-things go test ./...