refactor(yaml): simplify event declarations

[johanpel]

Description

Simplifies entity event declarations. Events default to once-cardinality and use multi: true when repeatable. Entity events and FSM states use attributes:, while records retain fields:.

Written by Codex.

Related Issues

This will also make additional syntax introduced by #427 across FSM and entity blocks consistent.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: QUIET

Plan: Enterprise

Run ID: 8515526d-20e5-4c16-ae18-e9d87c60c8b3

📥 Commits

Reviewing files that changed from the base of the PR and between fd9ef1a and 5262c68.

📒 Files selected for processing (6)

• crates/instrumentation-build/example/model.yaml
• crates/yaml/src/ast.rs
• crates/yaml/src/lower.rs
• crates/yaml/tests/diagnostics.rs
• crates/yaml/tests/fsm.rs
• crates/yaml/tests/references.rs

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📝 Walkthrough

Walkthrough

Event YAML declarations now use explicit multi and attributes fields. The AST and lowering logic were simplified accordingly, and diagnostics, reference, FSM, and instrumentation fixtures were updated to validate the new representation.

Changes

Event schema update

Layer / File(s)	Summary
Explicit event representation crates/yaml/src/ast.rs, crates/instrumentation-build/example/model.yaml	Event deserialization now uses a structured event with annotations, a boolean multi flag, and an attributes mapping; example event declarations use the new shape.
Schema event lowering crates/yaml/src/lower.rs	Event fields and annotations are lowered from the new structure, with multi selecting Cardinality::Multi or Cardinality::Once.
Validation and reference coverage crates/yaml/tests/diagnostics.rs, crates/yaml/tests/fsm.rs, crates/yaml/tests/references.rs	Tests validate boolean multi parsing, updated event fixtures, and expected cardinality for reference-related events.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Suggested reviewers: dhruv9vats, mbrobbel

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: simplifying YAML event declarations.
Description check	✅ Passed	It covers the change and related issue, and the missing Testing/Screenshots sections are non-critical.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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_{Comment @coderabbitai help to get the list of available commands.}

[mbrobbel]

Nice

[johanpel]

/merge