feat(cli): new Typer CLI; CLI-first docs; MCP base_url fix; examples via scripts

[AKKI0511]

Description

Introduce a production-ready Typer-based CLI with focused command groups, replace legacy CLI usage across docs, fix MCP base_url override behavior, align server logging with lifespan, streamline examples to run as standalone scripts, and update tests/CI accordingly.

Key Changes

• CLI
  • New agentconnect/cli/ Typer app with commands: version, config {init|show|validate}, serve registry [--host --port --reload], registry ping, mcp start agent-discovery [--registry-url], doctor.
  • Removed legacy agentconnect/cli.py.
  • Packaging: console script points to agentconnect.cli:app; deps updated.
• MCP
  • Health checks and tool calls respect injected RegistryAPIClient base_url override.
• Servers
  • Apply registry server log level during FastAPI lifespan to avoid runtime mismatches.
• Documentation (CLI-first)
  • Updated root and package READMEs to use CLI; kept a tiny “Developer note” for module-path runs only where relevant.
  • Sphinx docs synced to reference CLI (index/quickstart + CLI API pages).
• Examples
  • Removed global example runner; run scripts directly via python path/to/script.py.
• Tests/CI
  • Added CLI tests; removed/simplified unnecessary logging tests.
  • CI and Makefile use pytest -q to reduce noise.
• Packaging
  • pyproject.toml and lockfile updated.
• Changelog
  • Unreleased section updated for all above.

Breaking Changes

• Removed legacy agentconnect --example/--demo flow. Examples now run directly as Python scripts. No backward compatibility provided by design.

Documentation

• CLI usage: agentconnect/cli/README.md
• Servers documentation: agentconnect/servers/README.md
• MCP documentation: agentconnect/mcp/README.md