docs(channels): clarify message receipt evidence (#90063)

Co-authored-by: Peter Steinberger <steipete@gmail.com>

docs/docs_map.md

@@ -2361,6 +2361,7 @@ Do not edit it by hand; run `pnpm docs:map:gen`.
   - H2: Layout and names
   - H2: Provision ignored files
   - H2: Run repository setup
+  - H2: Session worktrees
   - H2: Snapshots, cleanup, and restore
   - H2: CLI
   - H2: Gateway methods
@@ -6907,6 +6908,7 @@ Do not edit it by hand; run `pnpm docs:map:gen`.
 - Route: /plugins/sdk-channel-outbound
 - Headings:
   - H2: Adapter
+  - H2: Delivery Evidence
   - H2: Existing outbound adapters
   - H2: Durable sends
   - H2: Compatibility dispatch

docs/plugins/sdk-channel-outbound.md

@@ -66,6 +66,15 @@ Only declare capabilities the native transport actually preserves. Cover
 each declared send, receipt, live-preview, and receive-ack capability with
 the contract helpers exported from this subpath.
 
+## Delivery Evidence
+
+A `MessageReceipt` records the result returned by a channel adapter. Concrete
+platform message identifiers show that the platform send path accepted the
+message; they do not prove that a recipient's device displayed or read it.
+Receipts without platform message identifiers are local receipt metadata only.
+Channels with read receipts or device-delivery state should track those facts
+through a separate channel-specific path.
+
 ## Existing outbound adapters
 
 If the channel already has a compatible `outbound` adapter, derive the
@@ -97,12 +106,12 @@ Runtime send helpers also live on `channel-outbound`:
 
 `sendDurableMessageBatch(...)` returns one explicit outcome:
 
-| Outcome          | Meaning                                                                                  |
-| ---------------- | ---------------------------------------------------------------------------------------- |
-| `sent`           | at least one visible platform message was delivered                                      |
-| `suppressed`     | no platform message should be treated as missing                                         |
-| `partial_failed` | at least one platform message was delivered before a later payload or side effect failed |
-| `failed`         | no platform receipt was produced                                                         |
+| Outcome          | Meaning                                                                                 |
+| ---------------- | --------------------------------------------------------------------------------------- |
+| `sent`           | at least one visible platform message was accepted by the platform send path            |
+| `suppressed`     | no platform message should be treated as missing                                        |
+| `partial_failed` | at least one platform message was accepted before a later payload or side effect failed |
+| `failed`         | no platform receipt was produced                                                        |
 
 Use `payloadOutcomes` when a batch mixes sent, suppressed, and failed
 payloads. Do not infer hook cancellation from an empty legacy