fix(error): align templates with Error Specification ADR

[yordis]

• Grounds the protobuf projection in the accepted Error Specification ADR instead of treating it as a standalone design.
• Keeps shared descriptors constrained to information that can cross publication boundaries safely.
• Gives runtimes and generators a shared reference for stable ErrorInfo fields before method-level outcome work.

[cursor]

PR Summary

High Risk
High risk because it changes the Visibility proto enum (removes VISIBILITY_INTERNAL and renumbers values), which is a breaking wire-level change for any stored/serialized descriptors or generated code relying on prior numeric values.

Overview
Aligns trogon.error.v1alpha1 docs and proto comments with the Error Specification ADR and the Google RPC rich error model, including a new Google RPC Error Templates guide and expanded runtime-mapping examples.

Updates error-template conventions to use lowerCamelCase metadata keys and proto JSON names, and clarifies that VISIBILITY_UNSPECIFIED is invalid for emitted details.

Makes a breaking change to proto/trogon/error/v1alpha1/visibility.proto by removing VISIBILITY_INTERNAL and renumbering VISIBILITY_PRIVATE/VISIBILITY_PUBLIC, and tweaks consistency/error docs to match the new metadata naming (e.g., projectionTimeout, minVersion).

^{Reviewed by Cursor Bugbot for commit ccd396d. Bugbot is set up for automated code reviews on this repo. Configure here.}

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⚙️ Run configuration

Configuration used: Organization UI

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Run ID: 57c47505-b4ee-4325-a51d-5c400080c2ff

📥 Commits

Reviewing files that changed from the base of the PR and between 41f48a0 and ccd396d.

📒 Files selected for processing (8)

• docs/README.md
• docs/explanation/consistency-pattern.md
• docs/explanation/google-rpc-error-template.md
• docs/explanation/protobuf-extension-naming.md
• docs/how-to/document-errors-in-proto.md
• proto/trogon/consistency/v1alpha1/consistency.proto
• proto/trogon/error/v1alpha1/options.proto
• proto/trogon/error/v1alpha1/visibility.proto

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch yordis/docs-google-rpc-error-template

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[github-actions]

The latest Buf updates on your PR. Results from workflow Buf CI / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	⏩ skipped	May 6, 2026, 5:42 AM

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit eefc63b. Configure here.}