[FEATURE] Let mods add a row to the desktop Session Rail

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The desktop Code tab's new Session Rail shows a session's state at a glance: Environment, Context, Connectors, Outputs. A mod can't add to it. The mod API in Claude Code 2.1.295 (the desktop app's bundled CLI) draws a Pane, the AbovePrompt band, a status entry, toasts and transcript components, but has no render site in the rail.

So a mod that tracks one piece of session state has to open a whole pane to say one line. My view-memory mod knows when a memory has a passed due date or a broken index. Today you see that only after running /view-memory.

Proposed Solution

A SessionRail render site, shaped like AbovePrompt:

• A ui.render hook on { component: 'SessionRail' } returns one row: a label, a short value, and an optional color (warning, success).
• The engine seats it below the built-in sections, one row per plugin.
• Pressing the row raises ui.press, so the mod can $.ui.open its own pane.
• next(e) with nothing to show draws no row.
• Surfaces without a rail never raise it, the way mobile has no Input.

Alternative Solutions

• A toast: it disappears, and raising it again each turn is noise.
• The AbovePrompt band: it takes rows above the prompt for state that only needs a glance.
• A pane opened unasked: it takes over the side area for one line.
• A status entry: text only, with no press to open the mod's pane.

Priority

Medium - Would be very helpful

Feature Category

Developer tools/SDK

Use Case Example

1. I'm deep in a long session in the Code tab.
2. A project memory has a due 2026-10-13 line, and the date passed.
3. The rail shows Memory 1 overdue in the warning color, under Context 78%.
4. I click it, the Memory pane opens on that item, and I deal with it before I /clear.

Additional Context

Claude desktop app 2.37337.1, Claude Code 2.1.295, macOS 27.0.1.