v0.4.1.0 feat: enable freeform LLM CAD generation (#15)

* feat: harden CAD intake and evidence pipeline

* docs: synchronize runtime contracts for v0.4.0.0

* feat: enable freeform LLM CAD generation

Allow arbitrary parametric OpenSCAD requests to use configured LLMs without silent template substitution, add bounded model diagnostics, and keep visual repair leases safe for delivered jobs.

* fix: preserve explicit model request deadlines

* test: handle blank model timeout configuration

* fix: remove default LLM generation timeout

Leave model requests unbounded at the application layer unless an operator explicitly sets AGENTSCAD_LLM_TIMEOUT_MS; caller cancellation and hosting-platform limits still apply.