docs(gfql): scope #1046 follow-on executable child slices - #1340

Summary

Follow-on scoping for #1046 after the completed #1262 T1-T5 program.

This PR:

• adds a committed scoping artifact describing the next executable child slices for the remaining public-facing native-type work
• links that scoping artifact from the GFQL AI guide
• records the scoping receipt in Development changelog

Child slices opened from this work:

• GFQL type system follow-on A: public declarative schema model + stable exports #1337 — public declarative schema model + stable exports
• GFQL type system follow-on B: schema inference API + typed topology extraction #1338 — schema inference API + typed topology extraction
• GFQL type system follow-on C: public schema-Arrow APIs + plottable boundary enforcement #1339 — public schema↔Arrow APIs + plottable boundary enforcement

Related:

• [FEA] GFQL native type system: schemas, inference, validation, and Arrow representation #1046 umbrella
• Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259 execution DAG
• Schema: Typed topology #483 typed topology

Files

• ai/docs/gfql/scoping_1046_follow_on_slices.md (new)
• ai/docs/gfql/README.md
• CHANGELOG.md

Validation

• bin/check_docs_latex_unicode.sh

Notes

No runtime code changes in this PR; this is scoping + coordination documentation.