fix: Update demo CLI to use ModelRegistry.resolve pattern (#228)

[andreasronge]

Summary

Replace legacy Map.get(presets, name) pattern with ModelRegistry.resolve/1 in the /model command handler of demo/lib/ptc_demo/cli.ex. This aligns with the pattern already used in JsonCLI and LispCLI.

Changes

• Updated handle_input("/model " <> name) function to use PtcDemo.ModelRegistry.resolve/1
• Replaced silent fallback behavior with explicit error handling
• Model resolution now validates against known presets and custom model aliases
• Consistent error messages when resolution fails

Closes #228

[github-actions]

PR Review: fix: Update demo CLI to use ModelRegistry.resolve pattern

Summary

Small tech-debt cleanup that aligns demo/lib/ptc_demo/cli.ex with the ModelRegistry.resolve/1 pattern established in PR #227. The implementation correctly mirrors the existing JsonCLI and LispCLI handlers.

What's Good

• Exact pattern match: The updated /model command handler at cli.ex:103-115 is identical in structure to json_cli.ex:126-138 and lisp_cli.ex:126-138, ensuring consistency across all CLI implementations
• Correct function choice: Uses ModelRegistry.resolve/1 directly rather than CLIBase.resolve_model/1 which would incorrectly exit the program on error (per issue discussion)
• Explicit error handling: Invalid model names now show clear error messages instead of silently passing through as raw strings
• Clean diff: Net zero lines changed, pure refactor with no scope creep

Issues (Must Fix)

None identified.

Suggestions (Optional)

None - the PR does exactly what's needed, no more, no less.

Security

No concerns. The change is internal to demo code and doesn't affect any validation logic.

Documentation

No updates needed. This is an internal refactor to demo CLI code; the public-facing behavior (model switching) is unchanged.

Verdict

Approve - Clean, mechanical change that brings cli.ex into alignment with the established pattern. The implementation matches the issue requirements exactly.

[andreasronge]

Auto-Triage Summary

Review Analysis

The automated PR review found zero issues requiring action:

• ✅ Must Fix: None
• ✅ Suggestions: None
• ✅ Security: No concerns
• ✅ Documentation: No updates needed

Verdict

Approve - Clean, mechanical change that brings cli.ex into alignment with the established ModelRegistry.resolve pattern from PR #227.

Status

• FIX_NOW items: 0
• Issues created: 0
• Items ignored: 0

This PR is ready to merge pending CI checks.