Declare the v2.* direct-call compat-arm exemption: one of two arms, measured at diagnostic identity

[gunbai-bot]

v1.compiler.infer module_skips_direct_call_arg_check returns true for
every module whose declared name begins with v2., and until this row that
exemption was declared nowhere in-tree. gunbc.doc_graph_roots already names
it as the one in-tree violation of the no-escape-hatch clause — the compiler
being bootstrapped is authored under weaker checks than ordinary source — and
records that its deletion (gunbc#8924) is CLOSED and held on a resolve-layer
seam whose repair was DECLINED on 2026-08-22 with no owner and no schedule.
That is an untracked stall wearing a trigger's costume (DESIGN §4b(2)): with
no row, there is no trigger, and a drop is retired BY ITS TRIGGER AND BY
NOTHING ELSE.

WHAT THE EXEMPTION SUPPRESSES, MEASURED RATHER THAN ARGUED FROM THE PREDICATE
NAME. One fixture authored twice, byte-identical but for its module line and a
renaming of every declaration so nothing resolves across the pair, run through
a gunbc built from this tree. Three arms each, all receiving a kernel String:
a local type Wrapped = FreeMonoid<Char> parameter, a cross-module
v2.std.text.String parameter, and an Int control.

non-v2. local alias ADMITTED, no diagnostic
declaration path REFUSED, inhabitance
Int control REFUSED twice: type mismatch + inhabitance
v2.* local alias ADMITTED, no diagnostic
declaration path REFUSED, inhabitance (same identity)
Int control REFUSED once: inhabitance ONLY

Exactly one diagnostic identity disappears across the pair — the type mismatch row — and every other identity is preserved. So this exemption
suppresses arg_compat_diags and nothing else. A count join would have been
defeated by the concat at 04_infer:5792 alone; identity is what makes the
difference attributable to the exemption rather than merely coincident with it.

THE LOSS IS NARROWER THAN THE PREDICATE'S NAME, AND THE FIRST DRAFT OF THIS
ROW GOT IT WRONG. arg_compat_diags is computed under the gate at :5769;
direct_call_argument_inhabitance_diags is called immediately after with NO
gate at :5780; both feed one concat. The inhabitance judgment therefore runs
inside v2.* exactly as it runs everywhere else (found by vivid-deer-102,
verified here at the source). A reader who takes argument checking to be off
in v2.* will misattribute every surviving refusal and every surviving
admission.

CONSEQUENTLY THIS ROW CLAIMS NO SELF-HOST HARM AND NAMES NONE. The specimen
anyone reaches for first — src/v2/std/integer.dag calling v2.std.text
string_head, whose emitted Rust rustc refuses — is NOT hidden by this
exemption: the surviving inhabitance arm judges that shape, and the fixture
shows the compat arm would not have refused it either. That shape belongs to
the already-standing text_boundary_identity_wall row. Citing it here would
be an unbacked execution claim.

The population is restated off the 9-declarations-under-formatters bound the
hold was priced against: the predicate's population is every module whose
declared name begins with v2., which includes the self-host emission
closure. The claim is not that the blast radius now exceeds 9 — it is that the
SUBJECT CHANGED and the old bound no longer describes what is being bought.

DESIGN.md and docs/design-ledgers.md are regenerated projections of
gunbc.rung_drop, not hand-edited.

The instrument

The fixture is described in the row in full rather than committed: two modules, byte-identical but for the module line, every declaration renamed so nothing resolves across the pair, three arms each, one gunbc run resolve per module against a gunbc built from this tree. It is re-derivable from the row's own text; committing a scratch probe with no final consumer would be §6 experimental residue.

What this does not do

• It does not repair the exemption. [HELD BY DECISION] Delete the v2.* direct-call argument-type exemption (cut B): the 19 refusals it reveals are two compiler seams, not source debt #8924 is the deletion and stays closed; this row makes the hold declared instead of untracked, so it can be retired by its trigger.
• It claims no self-host harm. That belongs to text_boundary_identity_wall.
• It does not touch the inhabitance arm, which is ungated and keeps its rung.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Vo22gFeUgs7vAVuhsmWqKk