[FEATURE] claude_code.tool spans don't identify which skill or agent was invoked

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When OTEL tracing is enabled (beta), claude_code.tool spans for Skill and Agent tool invocations only include the generic tool_name (e.g., "Skill" or "Agent"). The specific skill being invoked (e.g., "compose-render", "direct-creative-brief") is not present on the span.

The corresponding claude_code.tool_result log records do include the specific name via tool_parameters and tool_input attributes, but log records do not carry traceId or spanId, so they cannot be linked back to their span.

Current span attributes:

{
  "span.type": "tool",
  "tool_name": "Skill",
  "duration_ms": 6
}

Proposed Solution

Resolve tool_name to the actual skill/agent name instead of the generic wrapper name (e.g., "fix-docs" instead of "Skill").

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

Developer tools/SDK

Use Case Example

When building an observability dashboard over Claude Code sessions (e.g., tracking which skills are used most, measuring per-skill latency, building operation DAGs), the span tree is the natural data source it provides timing, parent-child relationships, and trace context.

However, with tool_name: "Skill" on every skill span, it is not possible to break down metrics by actual skill without falling back to log records, which lack trace linkage.

Additional Context

_No response_