M2-PR6: M2 exit-gate closure bundle + RF4 coverage accounting

[lmeyerov]

M2-PR6: M2 exit-gate closure bundle + RF4 coverage accounting

Parent: #1139

Objective

Close M2 with explicit evidence: exit-criteria checklist, RF4 accounting, and end-to-end conformance receipts.

Deliverables

• M2 exit-criteria checklist completed with concrete links/artifacts.
• RF4 M2-scope construct table mapped to:
  • implemented logical operator coverage, or
  • explicit deferred item + tracking issue.
• Differential corpus expanded and green for all M2 operator classes.
• Final verifier + planner + lowering-path conformance receipts collected.

Acceptance Criteria

• milestone-M2.md exit criteria satisfied and evidenced.
• M2 meta issue Metaissue: M2 execution DAG (PR1-PR6) + conformance gates #1139 is closable with links to all lane artifacts.
• No unresolved high-severity planner/verifier contract findings.
• CI green.

Non-goals

• M3 physical planner cutover.

References

• plans/compiler-refactor/milestone-M2.md
• plans/compiler-refactor/research/rf4-unsupported-scope-table.md

[lmeyerov]

Parent tracker: #1139.\n\nLane-specific testing expectations for PR6:\n- M2 exit criteria checklist completed with links to concrete artifacts.\n- RF4 unsupported construct table mapped to implemented operator or explicit defer issue.\n- Final differential + verifier/planner/lowering conformance receipts attached before close.

[lmeyerov]

Tracker sync after PR5 merge:\n\n- PR5 (#1147) is merged and #1128 is closed.\n- Remaining M2 closure work is now concentrated in this lane (#1137) plus #1135/PR #1142.\n\nSuggested execution order for closure:\n1. Finalize #1135/PR #1142 receipts\n2. Complete #1137 exit checklist + RF4 accounting + end-to-end evidence links\n3. Close metaissue #1139.

[lmeyerov]

M2 tracker sync after recent merges:\n\n- #1135 closed via #1142\n- #1128 closed via #1147\n\nThis issue (#1137) is now the sole remaining M2 closure lane.\n\nRecommended immediate execution:\n1. Assemble milestone-M2 exit checklist with links\n2. Attach RF4 implemented-vs-deferred accounting\n3. Add final differential/planner/verifier/lowering receipts\n4. Close #1137, then close #1139

[lmeyerov]

PR6 closure bundle is now implemented in PR #1151:
#1151

Canonical in-repo closure artifact:

• docs/source/gfql/spec/m2_exit_gate_closure.md

What is covered there:

1. M2 exit checklist with links to PR1-PR5 lane evidence
2. RF4 implemented-vs-deferred construct mapping
3. Local conformance receipts (planner/querygraph/verifier/cycle-policy + scope/alias rejection slices)
4. Merged lane CI rollup receipts for feat(gfql/m2): LogicalPlanner skeleton + op_id/IdGen contract #1129/feat(gfql/ir): LogicalPlan structural verifier (M2-PR3) #1131/feat(gfql/ir): QueryGraph extraction + cycle-policy regression locks #1142/feat(gfql/m2): route lowering metadata through LogicalPlan + escape-hatch reduction #1146/feat(gfql/m2): route CALL/GRAPH compatibility through LogicalPlan #1147
5. Deferred-item tracking issues:
   • Verifier follow-up: recursive LogicalType/ListType element validation #1153 verifier recursive ListType.element_type validation
   • M3 follow-up: expand LogicalPlan route coverage for deferred reentry/row-sequence Cypher flows #1154 M3 route coverage for deferred reentry/row-sequence logical-route flows

Current PR #1151 status:

• Targeted local conformance receipts: green
• GitHub checks: green/skipped except docs/readthedocs.org:pygraphistry still pending at time of comment

[lmeyerov]

Update: PR #1151 is now ready-for-review and all reported checks are complete (no failures; ReadTheDocs is now passing). Remaining action is merge PR #1151, then close #1137 and #1139 per the documented sequence.