Body-emit Track B: dissolve FLAG E row-fold + 3 hand-walker scaffolds (match/if/body_try) into the general body producer, Stage B cross-decl — make real compiler-corpus fn bodies become substrate behaviors (unblocks 12/13 emit-shape-gated tail modules)

[briansrls]

Auto-opened by session-dashboard for session cool-gull-618.
Pushing to session/cool-gull-618-body-producer-forward advances this PR.

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Summary

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[gunbai-bot]

Addressed both advisory findings from review 39443 in affedee6d:

1. Forward/fold identity parity — body_producer_forward_surface_identities() + body_lower_fold_behavior_surface_identities() with body_lowering_forward_fold_surface_identities_agree() enrolled in the fast-lane witness (wave1_gate1_a1_forward_fold_surface_identities_agree_witness_holds).

2. Identity-Absent match-spine dispatch — restored the deleted scaffold’s body_lower_match_capture_heads_spine → body_lower_try_match_from_captured path via body_lower_fold_identity_absent (wired into body_lower_fold’s Absent arm). Synthetic fixture witness proves spine sniff fires and dispatch does not silently reduce (wave1_gate1_a1_match_spine_identity_absent_dispatch_witness_holds).

— sent from cool-gull-618

[gunbai-bot]

Review 39446 — no code changes required; all points already hold on affedee6d:

• ForwardRowSelection / forward_row_select_step are gone from ingest; 03_ingest.dag delegates to grammar_relation_row_forward_token_spine_selection in v2.std.grammar (GrammarRelationForwardRowSelection single authority).
• Removed helpers (body_lower_try_if_from_node, body_lower_try_match_from_node) have zero live callers in src/v2/ (only historical mentions in plan docs).
• Catalog-edge skip (^grammar_relation_rules_formal_productions) is wired in grammar_relation_forward_row_select_skip_catalog_edge; edges without token spines would have been no-ops in the old fold too.
• Scaffold counter pinned at 0 with fast-lane witnesses (parity + match-spine dispatch added in affedee6d per review 39443).

— sent from cool-gull-618

[gunbai-bot]

Review 39448 — Findings: None acknowledged; no code changes required.

The described staging (forward row table vs body_lower_fold hardcoded dispatch; production-identity selection not yet at the normalize seam) matches the dissolve-on markers on affedee6d. Witness roster covers scaffold count=0, forward row count, surface-identity parity, and match-spine identity-absent dispatch.

— sent from cool-gull-618