Fix duplicate DOM ids in chat_ui tool-call partials

[edudepetris]

What this does

Fix #804

When an assistant message has multiple tool calls, the chat_ui tool-call partial renders each one with the same id because it uses the parent message's id instead of the individual call's id. That's invalid HTML (the id attribute must be unique in a document)

The bug only surfaces with parallel tool calls (multiple calls per message). Sequential calling produces one call per message, keeping ids naturally unique.

Use tool_call.id for the element id (it's unique and already available in the partial). Namespace ids with tool_call and tool_result prefixes to keep them distinct from message ids.

Before:

 <div id="message_78">  Called a_tool
 <div id="message_78">  Called b_tool   ← duplicate

After:

 <div id="message_tool_call_101">  Called a_tool
 <div id="message_tool_call_102">  Called b_tool   ← unique

before	after

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation
• Performance improvement

Scope check

• I read the Contributing Guide
• This aligns with RubyLLM's focus on LLM communication
• This isn't application-specific logic that belongs in user code
• This benefits most users, not just my specific use case

Required for new features

N/A — bug fix.

Quality check

• I ran overcommit --install and all hooks pass
• I tested my changes thoroughly
  • For provider changes: Re-recorded VCR cassettes (no provider changes)
  • All tests pass: bundle exec rspec
• I updated documentation if needed
• I didn't modify auto-generated files manually (models.json, aliases.json)

AI-generated code

• I used AI tools to help write this code
• I have reviewed and understand all generated code

API changes

• Breaking change
• New public methods/classes
• Changed method signatures
• No API changes

[edudepetris]

I moving this into draft until I verify that d0035b9 is working.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.48%. Comparing base (978d5f2) to head (d0035b9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #802      +/-   ##
==========================================
+ Coverage   88.47%   88.48%   +0.01%     
==========================================
  Files         122      122              
  Lines        5898     5898              
  Branches     1405     1405              
==========================================
+ Hits         5218     5219       +1     
+ Misses        680      679       -1     

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