Web Shell channel sessions in the sidebar

Motivation

Daemon-managed channels create ordinary workspace sessions with sourceType: "channel", but the Web Shell sidebar intentionally requests only the default session catalog. A session started from DingTalk, Feishu, or another channel therefore cannot be opened from the sidebar even though it is stored in the selected workspace.

Design

Add a two-option source switch above the sidebar's project session list:

• Tasks lists sourceType: "default" and remains the initial selection.
• Channels lists sourceType: "channel".

The switch is shown only when the daemon advertises session_source_metadata. Older daemons keep the current unfiltered request and do not show a control they cannot support.

The selected source is applied consistently to active, pinned, archived, and secondary-workspace session requests. Existing session rows, workspace sections, grouping, search, polling, and open-session actions are reused. Because channel sessions can be created by external messages without a Web Shell mutation event, the expanded Channels list uses the active-session poll interval instead of the 30-second idle interval.

When the selected workspace also advertises channel_management, the Channels catalog joins each session's immutable channel instance name (sourceId) to the current channel configuration and groups sessions by config.type. The type catalog supplies the platform label, so multiple instances of the same platform share one collapsible section. Sessions whose instance no longer exists remain visible under Other channels. If the catalog is unavailable, the list keeps its existing fallback instead of hiding sessions. Channel type grouping overrides user-defined session groups in the Channels view; Tasks keeps its existing organization behavior. Secondary workspaces resolve their own workspace-scoped channel catalog.

Channel adapters still prepend their model-facing instructions and contextual history. The daemon prompt carries the user-authored text separately as transcript display metadata, so live and replayed Web Shell messages do not expose that hidden context and channel session titles derive from the same visible text.

Boundaries

• Channel configuration and runtime management are unchanged.
• Session source metadata and daemon list APIs are unchanged.
• Session Overview and Split View keep their existing default-session scope.
• The switch is in-memory UI state and resets to Tasks on page reload.
• Channel type classification reflects the current workspace configuration; sessions do not persist a historical platform type.

Verification

• Assert the source switch is gated by session_source_metadata.
• Assert Tasks is initially selected and requests sourceType: "default".
• Assert selecting Channels requests sourceType: "channel" for primary and workspace-qualified lists.
• Assert the Channels list polls on the active-session interval.
• Assert multiple instances of one platform share a collapsible type section, other platform sessions remain separate, pinned sessions stay in their type section, and unmatched sessions remain under Other channels.
• Assert channel prompts preserve full model context while recording only the user-authored text for transcript display.
• Run the sidebar and workspace-section unit tests, Web Shell build, and TypeScript typecheck.