GrammarExpr → FormalProduction flat-list refactor across extdeps Wave-1/2a language files

[briansrls]

Summary

Adds canonical FormalProduction flat-list grammar carriers alongside existing GrammarExpr/GrammarRoot operational scaffolds across Wave-1/2a extdeps language files (cpp, go, java, kotlin, swift, typescript). Each file gains *_formal_production(s)() lists with choice/optional/repeat expanded via suffix nonterminals, matching the rust.dag CP-1b dual-carrier pattern. GrammarExpr trees remain until CP-1b converges parse onto the canonical substrate.

Test plan

• Rebased onto main (resolved go.dag status-line conflict with [codex] T-4.17 Go Wave 2b type deepening #3827 Wave 2b)
• cargo test -p v3-compiler (CI)
• cargo test --workspace (CI)

[briansrls]

Superseded by #3828 (valiant-boar-99). Stale duplicate from earlier spawn attempt.

[briansrls]

Verified against current HEAD (b7d04b3ae) and superseding branch session/valiant-boar-99 (#3828).

Duplicate finding: valid for the overlapping carrier pattern. #3828 already lands the Wave-1/2a FormalProduction flat-RHS scaffold across the full T-4.17 language set (cpp, go, java, kotlin, swift, typescript, rust, python, wasm, dag.dag) with the CP-1b dual-carrier hold. #3834's commits are a subset of that scope — no further merge path here.

One delta worth noting for #3828 (not blocking this close): this branch's kotlin_wave2_formal_productions / swift_wave2_formal_productions (~480/350 lines each) expand GrammarExpr wave-2 productions into flat multi-rule CFG; #3828 at HEAD only has wave-1 formal lists for those two files. If wave-2 flat lists are still wanted before #3828 merges, cherry-pick commits cb2fc2e66/217f89d0a onto session/valiant-boar-99.

No code changes on this closed PR. Merge readiness: N/A (closed, not merged).

— sent from crisp-koi-360

[briansrls]

Review metadata

• Provider / model: codex / unknown
• Commit: 0c8fdbcb · Trigger: schedule
• Thinking: 368s wall

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BLOCKING (1)

Root Cause

• src/v4/std/grammar.dag ParseGrammar remains the only consumed grammar boundary while FormalProduction is staged as a bare list → add a consumed FormalGrammar/FormalProduction carrier and derive canonical_symbols from it, or keep the flat lists out until CP-1b lands.

⚠️ The flat FormalProduction data needs to become the consumed language-model grammar authority, not an unconsumed parallel list.

[briansrls]

BLOCKING: kotlin_wave2_formal_productions introduces a second grammar authority whose formal-only suffix/opt nonterminals never flow into KotlinLanguageModel or canonical_symbols, which still consume kotlin_wave1_grammar, violating INVARIANTS P2 single-authority/facts-flow-forward.