docs: correct the ephemeral labels on four persisted session events

[examon]

docs/features/streaming-events.md marks four events as "Ephemeral." although all four are persisted to the session event log and are still present in a resumed session's history. This removes the incorrect classification.

The affected events are permission.requested, permission.completed, external_tool.requested and external_tool.completed.

Fixes #2171

Why these four are persisted

The file defines the term itself, which is what makes the label falsifiable:

| Ephemeral event | Transient; streamed in real time but not persisted to the session log. Not replayed on session resume. |

and gives the operational rule in the event-envelope table:

| ephemeral | boolean? | true for transient events; absent or false for persisted events |

None of the four carried the field in the sessions I ran, so by the file's own rule they are persisted. The generated event types agree. A genuinely ephemeral event declares a required literal (IdleEvent: ephemeral: true); three of these four declare the ordinary ephemeral?: boolean used by every other persisted event such as assistant.turn_start, and ExternalToolCompletedEvent declares ephemeral?: true — an optional literal, the only one in the generated types, which constrains the value only when the field is present. Current sessions do not emit it.

The labels were correct when the guide was added in #717. #1177 regenerated the types and moved all four off the required-literal shape in one commit; the prose was not updated with them.

What changed

Ten lines in one file, all deletions of the classification. Nothing else in the file was touched.

• The four event sections drop the leading Ephemeral. . The file's existing convention is that persisted events carry no marker, so this matches the 24 sections that are already unmarked, and no new wording is introduced.
• The two permission.* entries of the "agentic turn flow" diagram drop the trailing (ephemeral), matching the diagram's unannotated persisted entries.
• The four corresponding rows of the "All event types at a glance" table have the Ephemeral column cleared, matching the empty cell every persisted row already uses.

Before:

### `permission.requested`

Ephemeral. The agent needs permission to perform an action (run a command, write a file, etc.).

After:

### `permission.requested`

The agent needs permission to perform an action (run a command, write a file, etc.).

The glossary and the envelope table are untouched: they are the definitions these labels contradicted. The other 20 events marked "Ephemeral." in the file are correct and are unchanged.

Verification

A differential over the whole file compares three surfaces — every event section, every summary-table row, and every entry of the turn-flow diagram — against the ephemeral shape in the schema shipped with the pinned @github/copilot dependency, classifying an event as ephemeral only when the property is const: true and listed in the envelope's required.

	Sections	Table	Diagram
Before	4 mismatches	4 mismatches	2 mismatches
After	0	0	0

The mismatches before the change are exactly the four events above; no other event is affected in either direction. The check is deterministic across repeated runs.

Behaviour was confirmed separately with real sessions run against a local build of this branch: all four events appear in the session's event log and in the resumed session's history, while the session.idle and assistant.message_delta controls are correctly absent from both.

Documentation validation passes (scripts/docs-validation: TypeScript, Python, Go and C# all green locally; the Java leg needs Maven, which was unavailable in my environment). The change touches no extracted code block — the only fenced block it edits is the untagged diagram, which the extractor ignores — and the file's line count is unchanged, so no extracted block's reported line number moves.

Scope

Documentation only. No code, no generated file, no schema, no sample and no public API is affected.

One thing this does not do: nothing detects this kind of drift. The extractor only validates fenced code blocks, so prose claims about the event contract are unchecked and can go stale again the next time the classification changes. Comparing this file's Ephemeral column against the schema that already ships with the pinned dependency would be a small check, and I am happy to follow up with one if that is wanted.

[Copilot]

Pull request overview

Corrects documentation to classify four persisted session events accurately.

Changes:

• Removes incorrect “Ephemeral” labels from four event descriptions and summary rows.
• Updates the agentic turn flow diagram for permission events.

Show a summary per file

File	Description
docs/features/streaming-events.md	Corrects persistence classifications across reference sections, diagram, and summary table.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Medium