Merge remote app attribution branch

Resolve the RFC and implementation to defer OpenRouter-specific attribution headers and keep mandatory attribution to User-Agent only.

docs/core-data-structures/llm-streaming.md

@@ -26,9 +26,22 @@ Every adapter MUST obey these, and every consumer may rely on them:
 - **`usage` before `finish`, nothing after `finish`.** Defer both to the provider's end-of-stream marker so a trailing usage-only chunk can't violate the ordering.
 - **Tool-call `arguments` stay raw JSON strings end-to-end.** Partial fragments stream via `argumentsDelta`; a provider that hands back parsed objects re-stringifies at `block-end`.
 - **Two sanctioned error paths.** A failure may either THROW from `stream()` (transport/protocol errors) **or** end the stream with `finish {kind:'error'|'aborted'}` (provider in-band errors, for adapters that can't throw mid-stream). Consumers must handle *both*. The agent loop translates a finish-error/aborted into a turn error — it never logs a normal completed assistant message for a failed step.
+- **Every provider HTTP request carries the app-attribution header.** Adapters send `attributionHeaders()` (below) - the `User-Agent` baseline - and prove it with a wire-level test (mock server asserting the received header, or the library's header hook for a library-backed adapter).
 
 This contract is why two adapters exist as a deliberate pair: `dsh-llm-deepseek` (hand-rolled fetch/SSE) and `dsh-llm-pi-ai` (the same endpoint through `@earendil-works/pi-ai`). Two independent internals over one contract is what pinned the protocol down — the library-backed adapter can't throw mid-stream, so it exercises the finish-chunk error path the hand-rolled one might not.
 
+## `AppIdentity` — app attribution
+
+The static public application identity every adapter sends to providers ([`packages/llm/llm/src/attribution.ts`](../../packages/llm/llm/src/attribution.ts)). `attributionHeaders(identity?)` maps it to the standard `User-Agent` header only; OpenRouter-specific app attribution headers are intentionally not supported by this contract. The default `APP_IDENTITY` sources its version from the package manifest; every field is a public product fact - no secrets, paths, session ids, or per-user identifiers, and nothing per-request may influence the values. Rationale: [Mandatory `User-Agent` attribution](../rfc/implemented/architecture/2026-06-21-mandatory-app-attribution-headers.md).
+
+```ts type-equiv
+interface AppIdentity {
+  product: string
+  version: string
+  url: string
+}
+```
+
 ## `TokenUsage`
 
 Per-call token accounting. Counts are **disjoint**: `inputTokens` is uncached input only; cached input is reported separately, and billed input is the sum of the three. Adapters whose providers fold cache hits into a single prompt total (DeepSeek's `prompt_tokens`) subtract them back out.
@@ -49,7 +62,7 @@ interface TokenUsage {
 
 ## The seam
 
-`LlmAdapter` is the provider seam: subclass, implement `stream()`, register with `ctx.llm.registerAdapter(models, adapter)`. The `block-start` / `block-end` `index` correlation and the assembler together mean an adapter only has to emit well-formed chunks — block reassembly is not each adapter's problem. The consumer surface (`ctx.llm.stream()` / `streamBlocks()` / `generate()`) and the `llm/stream` waterfall are described in [architecture.md § The vocabulary](../architecture.md#the-vocabulary-dsh-llm).
+`LlmAdapter` is the provider seam: subclass, implement `stream()`, register with `ctx.llm.registerAdapter(models, adapter)`. The `block-start` / `block-end` `index` correlation and the assembler together mean an adapter only has to emit well-formed chunks — block reassembly is not each adapter's problem. The consumer surface (`ctx.llm.stream()`) and the `llm/stream` waterfall are described in [architecture.md § The vocabulary](../architecture.md#the-vocabulary-dsh-llm).
 
 `ContentBlockType` (the key set the `index`-correlated blocks carry) derives from `ContentBlockMap`: