fix(semconv): add latest GenAI semantic convention attributes

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Fixes #3515.

Adds constants for the latest OpenTelemetry GenAI message attributes:

• gen_ai.input.messages
• gen_ai.output.messages
• gen_ai.system_instructions

The existing gen_ai.prompt and gen_ai.completion constants are preserved for backward compatibility.

Tests updated in opentelemetry-semantic-conventions-ai/_testing.py.

Tested locally:

245 passed in 0.23s

Summary by CodeRabbit

• New Features
  • Added three new span attributes to semantic conventions: gen_ai.input.messages, gen_ai.output.messages, and gen_ai.system_instructions.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds three new legacy SpanAttributes constants—GEN_AI_INPUT_MESSAGES, GEN_AI_OUTPUT_MESSAGES, and GEN_AI_SYSTEM_INSTRUCTIONS—to align with updated OpenTelemetry GenAI semantic conventions, replacing deprecated gen_ai.prompt and gen_ai.completion attributes.

Changes

Cohort / File(s)	Summary
New GenAI Span Attributes Constants packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/__init__.py	Added three new SpanAttributes legacy constants mapping to gen_ai.input.messages, gen_ai.output.messages, and gen_ai.system_instructions namespaces.
Test Parametrization Updates packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/_testing.py	Extended TestSpanAttributesLegacyLLMNamesPresent parametrized assertions to validate the three new legacy-name constants and their expected mappings.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐰 Hops with delight through conventions so bright,
Old gen_ai.prompt bids farewell tonight,
Input and output, instructions now clear,
Structured messages bring semantics near! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Linked Issues check	❓ Inconclusive	The PR adds the three new attribute constants (gen_ai.input.messages, gen_ai.output.messages, gen_ai.system_instructions) required by issue #3515, but does not implement the structured message format or update instrumentation logic.	Clarify whether the constant definitions alone fully satisfy #3515's requirement to migrate instrumentation to use the new structured message format, or if additional work is needed.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly describes the main change: adding new GenAI semantic convention attributes to maintain alignment with the latest OpenTelemetry specification.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to adding the three new GenAI semantic convention attribute constants and their test cases as specified in #3515.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

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[coderabbitai]

🧹 Nitpick comments (1)

packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/__init__.py (1)

159-161: Consider moving these GEN_AI_* constants out of the legacy alias block.

Line 159-Line 161 are canonical GEN_AI_* names, but they currently live under Legacy LLM_* aliases. Keeping true legacy aliases and canonical constants in separate sections will make future deprecation/migration cleanup less error-prone.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In
`@packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/__init__.py`
around lines 159 - 161, The three canonical constants GEN_AI_INPUT_MESSAGES,
GEN_AI_OUTPUT_MESSAGES, and GEN_AI_SYSTEM_INSTRUCTIONS are currently placed
inside the "Legacy LLM_* aliases" block; move these canonical GEN_AI_*
definitions out of that legacy section into the main canonical constants area
(or create a separate "Canonical GEN_AI constants" section) so canonical names
are clearly separated from legacy aliases, while keeping any LLM_* alias
assignments below (or referencing the moved constants) to preserve
backward-compatible aliases.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In
`@packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/__init__.py`:
- Around line 159-161: The three canonical constants GEN_AI_INPUT_MESSAGES,
GEN_AI_OUTPUT_MESSAGES, and GEN_AI_SYSTEM_INSTRUCTIONS are currently placed
inside the "Legacy LLM_* aliases" block; move these canonical GEN_AI_*
definitions out of that legacy section into the main canonical constants area
(or create a separate "Canonical GEN_AI constants" section) so canonical names
are clearly separated from legacy aliases, while keeping any LLM_* alias
assignments below (or referencing the moved constants) to preserve
backward-compatible aliases.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d66b5513-eab7-44ad-a787-3acc10217c21

📥 Commits

Reviewing files that changed from the base of the PR and between b80f109 and ec62de1.

📒 Files selected for processing (2)

• packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/__init__.py
• packages/opentelemetry-semantic-conventions-ai/opentelemetry/semconv_ai/_testing.py