Need a better Razor error compilation DX

[joelmartinez]

Artifact Storage and Cleaning Recommendation (2025-12-15):

For compiled template diagnostics and generated outputs, adopt this artifact storage plan:

• Store Razor compilation artifacts in <docsRoot>/.chloroplast/artifacts/razor/.
• Before each build or template compile run, delete the entire artifacts/razor/ directory so it always only contains results from the latest build.
• Recreate the folder and write only the artifacts from the most recent run.
• Add (if missing) a .chloroplast/.gitignore file with * so nothing in .chloroplast gets committed even if parent .gitignore is missing or incomplete.
• Optionally, include a .chloroplast/README.txt explaining the folder is generated and safe to delete.

Rationale:

• This ensures that build artifacts are easy to discover and examine—paths in error messages are meaningful and local.
• Users are protected from accidental check-ins (and don’t have to manage growing disk usage).
• No unique “run id” or timestamp folders required; always the latest build's output, for predictable navigation and debugging.
• No need for optional flags or configuration—it's safe to be opinionated and automatic.

Acceptance Criteria

• razor compilation errors should have actionable information, which means the user should be able to clearly see the file location/path to pull up the generated file.