v8 stack 2/5: TurboModule spec and the JS surface

[dmurphy5]

The stack

Five PRs, each based on the one before it. This is 2/5.

	PR	Contents	Base
1	#23	toolchain, dependencies, and the ai.openspace rename	master
2	#24	TurboModule spec and the JS surface 👈	#23
3	#25	Android durable journal and TurboModule	#24
4	#26	iOS Swift TurboModule rewrite	#25
5	#27	docs and example app	#26

#22 stays open and untouched as the single-diff view of the same change.
Its tree and this stack's tip are byte-identical (tree f8404b0), so merging
either one produces exactly the same master. Review whichever is easier to
follow; merge one and close the other.

---

Defines the TurboModule spec and the v8 JS surface. This PR lands the contract
— the natives that back it arrive in the next two PRs in the stack.

What's in it

src/NativeRNFileUploader.ts is the codegen spec both platforms generate from.
Six methods and five event emitters replace the hand-rolled NativeModules
lookup and the DeviceEventEmitter string channels.

Variant payloads (upload options, terminal events, snapshots) are typed as
UnsafeObject in the spec because codegen can't model Partial<>,
intersections, or index signatures. The precise contracts live in src/types.ts
and are applied at the public boundary in src/index.ts, so callers still get
full types — the looseness stops at the codegen layer.

Three new methods make terminal outcomes recoverable rather than
fire-and-forget: getUnacknowledgedEvents/ackEvents read and drain the native
journal, and getAllUploads enumerates what the OS still knows about. Terminal
events carry eventId, type, timestamp, and — where the platform has them —
responseCode, responseBody, responseHeaders.

Two behavior fixes worth a look:

• A scoped addListener now drops events it can't attribute, instead of failing
  open and delivering another upload's event to your handler.
• The iOS keep-alive hack that called native addListener on import is gone;
  the codegen emitters need no priming.

Adds jest and the first JS test suite, wired into CI and the pre-commit hook.

Reviewing this in the stack

The JS here calls TurboModuleRegistry.getEnforcing, so the new methods have no
implementation until PRs 3 and 4 land. That's inherent to slicing this way —
codegen reads the spec, so the spec has to come before the natives that extend
it. The stack is runtime-complete at its tip.

Verified

yarn typecheck, yarn lint:ci, and yarn test (7/7) pass on this commit.

Breaking

Requires the New Architecture. completed now fires only for 2xx or a request's
acceptStatus; other HTTP responses arrive as error with errorKind: 'http'
and the response attached.