QualifiedName de-fork: v2 authority = FreeMonoid<Symbol> + v1 seed bridge made generic

[gunbai-bot]

QualifiedName de-fork (v2 authority + v1 seed realization)

Dissolves the hand-rolled QualifiedName coproduct into the single FreeMonoid<Symbol> authority. Re-scoped from the original "v2-only" brief — investigation proved that premise false: the v1 Rust seed hardcoded QnEmpty/QnCons in host builtins (construct + consume + emit), so this is necessarily a v2-authority + v1-seed-realization de-fork.

v2 .dag

• type QualifiedName = FreeMonoid<Symbol>; deleted the hand-rolled trio (qualified_name_eq/for_all/singleton) → FreeMonoid ops + structural ==.
• Migrated ~22 consumers (QnEmpty/QnCons→Empty/Cons, eq→==, for_all→algebra for_all).
• Two recursive-tail raw-match sites (qn_fold_step, layer_prefix) rewritten to the list_head idiom — see resolver-gap note below.

v1 seed — no longer knows QualifiedName/QnEmpty/QnCons as a domain

The three QualifiedName-specific host builtins are now generic FreeMonoid<Symbol> marshaling (type_name FreeMonoid, variants Empty/Cons):

• qualified_name_value_from_dotted_string → free_monoid_symbol_value_from_dotted_string
• qualified_name_value_to_module_path → free_monoid_symbol_value_to_dotted_string
• emit_qualified_name_dag → free_monoid_symbol_emit_dag
  All callers (coproduct_reflection, external_authority_project ×7, v1_interpreter) updated. Bounded: no resolver changes, no broad cli_run cleanup. The .dag-facing std fn name is kept (it returns a generic FreeMonoid<Symbol>).

Verified by execution (rebuilt seed)

• Structural == gate green + discriminating (freemonoid_eq_witness_test.dag): equal→true, differing/prefix/empty→false, no native/modeled straddle.
• Dotted-string round-trip green through the generic seed bridge; layer_prefix green.
• External-authority corpus witnesses green (exercises the 7 seed-consumer sites).
• Rust manifest emit round-trip test green (3/3).
• Full-corpus compile-clean gate (primary-precedence): pending (running locally).

Resolver-gap note (docs corrected)

#5552 fixed simple generic-alias instantiation (construct/match/use-site). Raw variant-matching a value bound from a recursive Cons.tail field still hits "variant not found in type FreeMonoid" (04_infer gap) — avoided here via the list_head/algebra idiom that all FreeMonoid consumers already use. fold-ergonomics.md, dag-v2-defork-audit.md (+ .dag twin) corrected.

Net concepts drop

Old QualifiedName coproduct + helper trio removed; no new parallel authority (the seed helpers are generic FreeMonoid marshaling, not a QualifiedName bridge).

🤖 Generated with Claude Code

[gunbai-bot]

Local full-corpus compile-clean gate: PASS.

Since the ci job hits the by-design dark-CI 30-min cap (below the ~47min floor) and can't surface a compile-clean verdict, I ran the authoritative gate locally to completion:

gunbc run --entry dag/tools/floor_effect_gate_witness.dag \
  --function dag_compile_clean_gate_passes --claim-run
→ running dag_compile_clean_gate_passes()... true   (exit 0)

That is the exact floor gate (compile --source-root dag --source-root src/v2 --dependency-pool-index primary-precedence --target dag) — 0 compile errors corpus-wide with this migration. rust_tests is already green in CI, covering the v1 seed de-fork (host-builtin rename + manifest emit round-trip).

So the only red signal on this PR is the structural dark-CI timeout, not a real failure.

— sent from smart-crab-896