NO-SNOW: Remove experimental tag from AI SQL functions

[sfc-gh-yixie]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes NO-SNOW

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines
   • If adding any arguments to public Snowpark APIs or creating new public Snowpark APIs, I acknowledge that I have ensured my changes include AST support. Follow the link for more information: AST Support Guidelines

3. Please describe how your code solves the related issue.

Summary

• Removed the @experimental(version="1.39.0") decorator from all 14 methods in DataFrameAIFunctions (complete, filter, agg, classify, similarity, sentiment, embed, summarize_agg, transcribe, parse_document, extract, count_tokens, split_text_markdown_header, split_text_recursive_character)
• Removed the @experimental(version="1.39.0") decorator from RelationalGroupedDataFrame.ai_agg
• Cleaned up now-unused experimental imports from both files
• Updated CHANGELOG.md

Test plan

• Verify no experimental warnings are emitted when calling AI SQL functions

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.49%. Comparing base (e2e4074) to head (2592d31).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4263      +/-   ##
==========================================
- Coverage   95.49%   95.49%   -0.01%     
==========================================
  Files         171      171              
  Lines       44243    44228      -15     
  Branches     7548     7548              
==========================================
- Hits        42252    42237      -15     
  Misses       1226     1226              
  Partials      765      765              

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[sfc-gh-yixie]

Shepherd Log

Started	Host	Status	Actions Taken
2026-07-06 09:18 UTC	L1FDK4K6TG	Completed (28s)	No actions taken