Add repository agent guidance

[apstndb]

Summary

• Add .gitignore entries for local scratch space, editor metadata, macOS metadata, and the local spannerplanviz build output.
• Add AGENTS.md with repository-specific guidance for coding agents.
• Add CLAUDE.md as a thin pointer to AGENTS.md.
• Configure Gemini Code Assist repository review comments to HIGH severity or above via .gemini/config.yaml.
• Replace two Mermaid renderer WriteString(fmt.Sprintf(...)) calls with fmt.Fprintf to satisfy the current golangci-lint/staticcheck rule.

Validation

• go test ./...
• mise x -- golangci-lint run --timeout=5m

Reference

• Gemini Code Assist repo review configuration: https://developers.google.com/gemini-code-assist/docs/customize-repo-review

[gemini-code-assist]

Code Review

This pull request introduces documentation for AI agents in AGENTS.md and CLAUDE.md, detailing the project architecture and development workflows, and initializes a .gitignore file. The review feedback suggests adding the compiled binary to the ignore list, following Go idioms by removing the 'Get' prefix from getter methods, and using the %w verb for error wrapping to facilitate error inspection.

[Copilot]

Pull request overview

Adds repository-level guidance for coding agents and tooling configuration. The PR introduces an AGENTS.md reference document, a CLAUDE.md pointer to it, a .gitignore for local artifacts, and a .gemini/config.yaml to raise Gemini Code Assist's review severity threshold. The unrelated diff in visualize/mermaid.go (switching sb.WriteString(fmt.Sprintf(...)) to fmt.Fprintf(&sb, ...)) appears in the context but is not mentioned in the PR description.

Changes:

• Add AGENTS.md (with CLAUDE.md pointer) describing project architecture, commands, and conventions for coding agents.
• Add .gitignore for scratch space, editor/OS metadata, and the local build binary.
• Add .gemini/config.yaml setting comment_severity_threshold: HIGH.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
AGENTS.md	New agent-facing repo guide covering architecture, commands, and conventions.
CLAUDE.md	One-line pointer (@AGENTS.md) so Claude reuses the shared guidance.
.gitignore	Ignore .tmp/, .DS_Store, .idea/, and the spannerplanviz build output.
.gemini/config.yaml	Restrict Gemini Code Assist comments to HIGH severity or above.
visualize/mermaid.go	Refactor two sb.WriteString(fmt.Sprintf(...)) calls to fmt.Fprintf(&sb, ...) (not mentioned in PR description).

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[apstndb]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces comprehensive documentation for AI coding agents in AGENTS.md and CLAUDE.md, updates the .gitignore file, and refactors string formatting in visualize/mermaid.go. The review feedback suggests modernizing the AI terminology in the documentation and clarifying the role of build_tree.go to include node formatting logic.

[apstndb]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces documentation for AI coding agents in AGENTS.md and CLAUDE.md, updates the .gitignore file for local development, and refactors string formatting in visualize/mermaid.go to use fmt.Fprintf. Feedback indicates that a configuration file mentioned in the pull request description is missing from the current changes.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.