fix(framework): leave model selection to the user

[alexsoyes]

🎯 What & why

Bundled skills and agents override the user’s model with Sonnet or Opus. Remove those presets so execution uses the host’s model configuration.

🛠️ How it works

Remove model fields from five dev skills, both dev agents and the agent scaffold. Agent generation accepts a model only when the user requests one. Remove the marketplace tier table. General guidance on selecting lightweight agents and the token-optimization recipe stay unchanged. The evaluation harness passes --model only when explicitly supplied.

Telemetry records, provider schemas and compatibility fixtures retain model identifiers because they describe data or supported formats.

🧪 How to verify

• node --test scripts/__tests__/model-selection.test.js: 3 passing tests; two reproduced the forced defaults before removal. The harness tests use a stub CLI and spend no tokens.
• pnpm exec lefthook run pre-commit: 557 passing tests; documentation checks pass.
• node scripts/check-architecture-rules.js: 352 governed files, zero violations.
• Push hooks: CLI knip passes; CLI suite has 6,836 passing tests and 1 skipped.

✅ I certify

• I DO CERTIFY I READ EACH LINE OF THE PULL REQUEST BECAUSE I AM A SOFTWARE ENGINEER, NOT A AI PUPPY.