fix: reject unsupported DELETE LIMIT

[ryux1]

Which issue does this PR close?

• Closes BUG: DELETE with a LIMIT clause ignores the LIMIT and deletes every matching row #24998.

Rationale for this change

DELETE with LIMIT currently appears to plan successfully, but the table provider receives only the filters and deletes every matching row. Rejecting the unsupported clause prevents a bounded delete from silently becoming an unbounded one and matches the existing UPDATE LIMIT behavior.

What changes are included in this PR?

• reject DELETE LIMIT during SQL planning
• remove the unreachable limit construction from delete_to_plan
• replace the misleading EXPLAIN snapshots with error regressions, both with and without WHERE
• directly cover both planner rejection branches in the SQL integration suite

What is the testing strategy for this PR?

• cargo test -p datafusion-sqllogictest --test sqllogictests -- delete
• cargo test -p datafusion-sql --lib (88 passed)
• cargo test -p datafusion-sql --test sql_integration plan_delete_rejects_limit (2 passed)
• cargo clippy -p datafusion-sql --all-targets -- -D warnings
• cargo fmt --all -- --check

Are there any user-facing changes?

Yes. DELETE statements containing LIMIT now return a not-implemented planning error instead of accepting the limit and potentially deleting every matching row. There is no public Rust API change.

Implementation and validation were completed with AI coding assistance under the account owner’s direction.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.69%. Comparing base (d25ffaa) to head (380ddd3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #25005   +/-   ##
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  Coverage   81.69%   81.69%           
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  Files        1126     1126           
  Lines      415193   415188    -5     
  Branches   415193   415188    -5     
=======================================
- Hits       339182   339181    -1     
+ Misses      56079    56077    -2     
+ Partials    19932    19930    -2     

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