feat(ecs-mcp-server): add hosted MCP server documentation and registry metadata

[nineonine]

Summary

Changes

• Add server.json metadata file used for publishing ECS hosted MCP to the Official MCP Registry
• Update README to announce new hosted MCP server offering from ECS
• Fix package name build script to allow for optional dependency names. We use the mcp-proxy-for-aws in the hosted setup which is called out in the README

User experience

Users can now setup the ECS MCP server with a hosted option, eliminating local infra

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• I have reviewed the contributing guidelines
• I have performed a self-review of this change
• Changes have been tested
• Changes are documented

Is this a breaking change? N

RFC issue number:

Checklist:

• Migration process documented
• Implement warnings (if it can live side by side)

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.42%. Comparing base (d6344f8) to head (9f1c066).
⚠️ Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1875      +/-   ##
==========================================
- Coverage   90.42%   90.42%   -0.01%     
==========================================
  Files         851      851              
  Lines       63317    63317              
  Branches    10253    10253              
==========================================
- Hits        57256    57254       -2     
  Misses       3772     3772              
- Partials     2289     2291       +2     

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[nineonine]

The failing Python / Build ecs-mcp-server check will be fixed when #1870 is merged (the change in scripts/verify_package_name.py )

[lewisct]

A couple context questions as I ramp-up.