feat: improve tabular SK large result handling

[Paul Lizer (paullizer)]

Summary

This PR improves Tabular Semantic Kernel analysis by adding safer large-result handling and Python runtime compatibility on top of the current Development tabular pipeline.

Changes include:

• Adds pagination metadata for row-returning tabular tools: start_row, page_size, has_more, and next_start_row.
• Preserves explicit return_columns projection and protected row metadata such as _sheet, _matched_columns, _matched_values, _matched_on, _matched_source_values, and _related_document_reference_values.
• Adds safe row payload trimming for oversized tool results without skipping rows during continuation.
• Raises tabular SK computed-results handoff guardrails to 100K characters with warning logs on truncation.
• Keeps current Development model-context routing instead of reintroducing older direct endpoint wiring.
• Updates public @kernel_function tabular tool parameters to avoid Annotated[Optional[str], ...], preserving compatibility with both Python 3.12 and Python 3.13.

Attribution

This work is inspired by and adapted from the intent and design direction in these PRs by vivche:

• fix: Tabular SK analysis: multi-endpoint DeploymentNotFound 404 and Python 3.13 Optional[str] type error (#891) #892 by vivche: Tabular SK multi-endpoint investigation and Python 3.13 Semantic Kernel Optional[str] parameter compatibility.
• feat: Tabular SK analysis — pagination, auto-trim, return_columns forwarding, and 100 K handoff limit (#893) #894 by vivche: Tabular SK pagination, return_columns forwarding, automatic large-result trimming, and a larger computed-results handoff guardrail.

The implementation here was rebuilt against the current Development branch to preserve newer model-context routing, related-document evidence, generated tabular outputs, and thought tracking.

The commit includes this co-author trailer for attribution:

Co-authored-by: vivche <214204244+vivche@users.noreply.github.com>

Thank you vivche for surfacing the problems and proposing the original direction.

Documentation

Added:

• docs/explanation/features/v0.242.067/TABULAR_SK_LARGE_RESULT_PAGINATION.md
• docs/explanation/fixes/v0.242.068/TABULAR_SK_PY313_KERNEL_PARAMETER_FIX.md

Updated:

• docs/explanation/features/index.md
• docs/explanation/fixes/index.md

Tests

Verified locally:

• py_compile on modified Python modules and modified functional tests.
• functional_tests/test_tabular_kernel_parameter_annotations.py: 1/1 passed.
• functional_tests/test_tabular_large_result_pagination.py: 5/5 passed.
• functional_tests/test_tabular_large_result_handoff.py: 2/2 passed.
• functional_tests/test_tabular_relational_analysis_helpers.py: 12/12 passed.
• functional_tests/test_tabular_related_document_evidence.py: 7/7 passed.
• get_errors: no diagnostics on touched files.
• git -c core.whitespace=blank-at-eol,blank-at-eof,space-before-tab,cr-at-eol diff --check: passed.

Notes

This PR intentionally does not include the unrelated ServiceNow docs/spec changes that were bundled in the source PR branches.