Reconcile reliable execution documentation

docs/consumers/pkg-promptkit.md

@@ -201,6 +201,10 @@ repair-call, duration, and presence-aware usage totals. Its usage is an
 aggregate, not an additional billable attempt. A known zero differs from an
 unknown count, and incomplete totals must not be treated as complete cost
 accounting. A failed operation still returns no partial `RunResult`.
+An injected client that leaves `UsagePresence` nil can report known nonzero
+counts, but its zero counts remain unknown to observations; supply explicit
+presence when measured zeros matter. Existing `RunResult.Usage` sums returned
+values independently of observation presence.
 
 Callbacks run synchronously, in order for one operation, and can overlap for
 different operations. Synchronize shared callback state and avoid blocking on
@@ -208,6 +212,9 @@ work that needs the same run's admission slot. Callback panics propagate;
 there is no durable event history or promise of a terminal event after panic.
 Events omit content and error objects, but selected identifiers may still be
 sensitive. See the [observation GoDoc](../../observations.go) for exact fields.
+The [offline proposal and assessment example](../../examples/go-library/observe/main.go)
+shows application-owned event collection and a separate semantic acceptance
+decision using the built-in HTTP path without network access.
 
 ### Repair A Structured Result
 
@@ -240,6 +247,9 @@ previous single-attempt behavior, or set `RunRequest.TransientRetries` to
 override one execution. A custom HTTP transport still uses this policy;
 injected `LLMClient` implementations retain their own retry policy. Application
 semantic retries are separate runs and can multiply provider traffic further.
+The caller context covers capacity and retry waiting as well as attempts;
+without a deadline a valid provider delay can be long. Promptkit does not
+infer exactly-once or complete cost accounting from a retry outcome.
 See the [provider integration contract](../integrations/openai-compatible-chat.md#transient-status-retries)
 for eligible statuses, waits, timeouts, and provider timing.
 
@@ -612,6 +622,12 @@ decoded or an injected client returns a nil successful response. Both retain
 `errors.Is` and `errors.As`. Caller cancellation and deadlines retain their
 standard context identities. Arbitrary injected-client errors retain their own
 identities without Promptkit guessing a failure category from their text.
+An eligible built-in status that consumes a positive retry budget additionally
+matches `ErrRetriesExhausted`; use `errors.As` to read
+`RetryExhaustedError.Attempts()` and the final `GenerationError` status. With
+explicit zero retries, the first eligible status is an ordinary generation
+error, not exhaustion. Completed structural rejection remains a normal result
+with failed validation, while an operational error returns no partial result.
 
 ## Application Boundary