fix(scripts): ADR-0087 gate reads an any index signature (D8 p4) and a src/index.tsx entry (D9) (#26496)

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Part of #26220 (PR 2 of 2 for parts 3 and 4: the gate code for the
ADR-0087 amendment that landed in #26455).

Clause-②: no
Metadata-protocol: none

## What changes

`scripts/check-adr-0087-registration.mjs` only (+288 / −11).

- **Part 3: predicate 4 reads an `any` index signature (D8, amended).**
When the base surface is concrete, a bare `<path>#<Symbol>` naming an
exported `interface`, or a `type` alias whose right-hand side is one
object type literal, now goes through `indexSignatureLimb`. The limb
holds when all three hold: (1) at the merge base an index signature's
value type is `any`; (2) at HEAD at least one of those carries another
value type, with `unknown` counted as narrowed here only; (3) the kind,
the heritage (type parameters, `extends`) and every member are identical
position by position on the comment-masked, normalised surface. Only the
value types of base-`any` index signatures are set aside, so a re-typed
non-`any` index signature is a moved member, which reads no wider than
the ADR text. A dotted member path does not reach the limb. When the
limb fails, the existing #6048 refusal now also prints why the limb did
not hold, e.g. "the member count moved (2 -> 1)".
- **Part 4: the D9 entry may be `src/index.tsx`.** `sourceEntryAt` maps
`dist/index.d.ts` (or its twin) to the package's one source entry,
`src/index.ts` or `src/index.tsx` (`SOURCE_ENTRY_NAMES`). Both present
is refused as AMBIGUOUS by name. Neither present is refused as
unmappable, as before. The build tool is never read.
- New helpers, exported for the unit pins: `structuralDeclarationParts`,
`readIndexSignature`, `indexSignatureLimb`. The member splitter does not
treat the `>` of `=>` as a closer, so a nested literal's index signature
is never read as a top-level one.

## Battery rows

New battery `IX (#26220): predicate 4 reads an any index signature; the
entry may be src/index.tsx`, 52 cases, roster floor 56 → 57:

- Predicate 4, green: IX-G1 #26293's shape (`[key: string]: any` →
`unknown` on a generic interface; the verdict names both sides) and
IX-G2 an object-literal alias with a `readonly` index signature narrowed
to `string`.
- Predicate 4, red, each with predicate 4's FALSE refusal and the limb's
reason:
  - R1 a member removed beside the narrowed signature (the #6048 class);
  - R2 a member re-typed;
  - R3 a member made optional;
  - R4 a type-parameter default changed;
  - R5 an `extends` added;
  - R6 a non-`any` base signature re-typed;
  - R7 a base signature typed `unknown`;
  - R8 still `any` at HEAD;
  - R9 the signature's key changed;
  - R10 an intersection alias;
  - R11 a nested `any` signature behind an `=>`;
  - R12 a dotted path.
- Units: IX-U1–U4 (the index-signature reader, mapped and computed names
refused, the compared parts, and the #6048 shape failing the limb).
- D9: IX-T1 a `src/index.tsx`-only package retires an export (green; the
verdict names `Gone.tsx`). IX-T2 both entries present is red as
ambiguous; its `.ts` twin exports the same names, so only the refusal
holds it red. IX-T3 neither entry is red as unmappable.

## Ablations

One-time, on the committed fix, each restored with `git checkout HEAD
--` (blob hash re-checked):

| ablation | failures | turns red |
| --- | --- | --- |
| limb call off | 3 | IX-G1, G1b, G2 |
| `=>` guard off in the splitter | 3 | IX-R11 goes green |
| set aside every index signature, not only base-`any` | 6 | IX-R6, R7
go green |
| heritage comparison off | 6 | IX-R4, R5 go green |
| `src/index.tsx` dropped from the entry names | 4 | IX-T1, T1b, T2 |
| ambiguity refusal off | 3 | IX-T2 goes green |
| dotted exclusion off | 1 | IX-R12's message; it stays red because the
limb reads no member path, so the exclusion is a stated guard rather
than the only one |

## Proof on the held PRs

With this branch's gate, `--base origin/main --head <their head>`:

- **#26293 at `e349c832`: exit 0.** The verdict is
`ui/packages/types/src/base.ts#ComponentRendererProps ([key: string]:
any -> [key: string]: unknown)`. Main's gate refuses it at predicate 4.
- **#26365 at `20d75f11`: exit 1, on a refusal the amendment does not
cover.** Main's gate refused all three operands at the MERGE BASE as
unmappable (`src/index.tsx`). With this branch the base side maps and
reads. The new refusal is at HEAD: "no workspace manifest at … is named
`@object-ui/plugin-ai`". #26365 deletes the whole package, and D9
predicate 1 reads "absent at HEAD" through a Program over the package's
entry at each rev, which a deleted package does not have. Admitting a
whole-package removal needs its own D9 wording (Tier H). Seat 1 has put
that choice to the maintainer, and it is not in this PR.

## Tests and gates

- `node scripts/check-adr-0087-registration.mjs --self-test`: exit 0,
"627 assertions over real temp git repos" (575 before this branch).
- `node scripts/pm/dispatch-gates.mjs --commands --repo
objectstack-ai/objectstack`: 34 commands derived at this head (base
`d0a7e748`). All 34 exit 0, including `--base origin/main` and
`--self-test` of this gate, `check-scripts-symbol-anchors`,
`check-declaration-mirrors`, `check-self-test-wired`, `pnpm
check:changeset-gate-self-tests` and `pnpm check:pm-dispatch-gates`.
`--ran`: 34 derived, 34 run, 0 NOT-MEASURED, 0 UNRUN.
- No package is touched, so there is no build closure and no changeset
(`skip-changeset`).

## Acceptance notes

- Part 3 and part 4 follow the amendment text of #26455 line by line.
The one place this code reads narrower than the text is condition 3:
only base-`any` index signatures have their value types set aside, so a
non-`any` one that changes is a re-typed member. This is stated in the
function's comment and pinned by IX-R6 and its ablation.
- #26324 (predicate 2 cannot certify an operand named `default`) is a
separate card and is not addressed here.

---
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Co-authored-by: Claude <noreply@anthropic.com>

Author: objectstack-fleet[bot]