Apply review feedback from PR #3459, correcting statements that
diverged from actual SDK behaviour and house conventions.

- Correct the retry-supersede edge case: a retry supersedes the prior
  attempt the moment it calls step.start(), because supersede keys on
  the fresh higher-serial ai-step-start under the same stepId, not on
  any output the retry produces.

- Qualify Realtime-client sharing as same-process only; Temporal and
  Vercel Workflow DevKit isolate each activity in its own process, and
  clarify that session objects must not be shared across activities.

- Use key: process.env.ABLY_API_KEY instead of authUrl in server-side
  and agent code samples, where an API key is the correct credential.

- Reference session.end()/session.detach() rather than the
  non-existent session.close() on AgentSession.

- Add 'cancelled' to the terminal StepEndReason list.

- Use "realtime" (one word) per house style.

- Align the AI Transport SDK version to the two-part '0.5' format used
  by sibling entries in languageData.ts.

Clarify the auth guidance so agents stop rewriting valid server-side
code, and add the "realtime" spelling rule that was previously only
enforced by hand.

- Principle 17 now states the client/server split explicitly: browser
  code uses authUrl, but server-side and agent code (activities, agent
  routes, workers) must use key: process.env.ABLY_API_KEY. An authUrl
  in a server snippet is a bug, not a pattern to preserve.

- Note why the client-key verification grep passes process.env-sourced
  keys, so the exception is visible at the check itself.

- Add "realtime" (one word) as an enforced spelling, with a sweep grep
  in the verification block.

Two documentation-wide accuracy fixes against @ably/ai-transport v0.5.0.

AgentSession no longer has close(): teardown is end(), which closes any
still-open Run as `cancelled` then detaches. detach() alone is reserved for
durable cross-process handoff. Every agent-side example that tore down with
session.close() now uses session.end(), and the connections concept describes
the ClientSession/AgentSession teardown split correctly. Client-side
ClientSession.close() is unchanged.

StepEndReason is `complete` | `failed` | `cancelled`: a cancel arriving while a
Step is open closes ai-step-end{cancelled} before the Run ends. The Steps
concept, the AgentSession step-end reference (including the end() default
derivation), and the wire-protocol step-reason header and ai-step-end rows now
list all three. The Run-level run-reason (RunEndReason) is left as
complete/cancelled/error.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

A write-docs review pass over the Vercel WDK pages tightened wording and
corrected two mechanism descriptions that misstated how the SDK behaves.

On the framework page, the supersede explanation attributed the prompt-ordering
guarantee to a "short wait" and said the publish ack does not guarantee it. The
guarantee is awaiting step.start(): it folds the superseding, higher-serial
ai-step-start into the read model behind run.view before it resolves, so reading
the view straight after is already clean. The cancel edge case claimed a later
cancel is replayed from channel history when load() resolves; cancels route only
through the live channel subscription, so the text now matches the SDK and demo.

The rest is phrasing: "realtime" spelling, a de-duplicated "owns its half of the
job" metaphor, an active-voice bullet, and a fifth Explore-next link.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>