Merge pull request 'docs(maestro): replace the sidebar's activity dot with a rail' (#130) from indicators into main

Reviewed-on: #130

docs/SIDEBAR.md

@@ -37,23 +37,45 @@ itself is not.
 Line 2 reads left to right:
 
 ```
-<dot> [<duration>] [<detail>] [<diff stat> | exited] <command>
+[<duration>] [<detail>] [<diff stat> | exited] <command>
 ```
 
-Its minimum content is therefore the dot and the command.
+Its minimum content is therefore just the command.
 
-`<dot>` is a single filled glyph (`●` on both clients) carrying the activity
-state's colour, and `<duration>` follows in the same colour when shown. There
-is no state word and no second badge: the dot exists so the state is still
-legible when a row is dimmed or the terminal renders the duration in the
-default fg. The dot is an unconditional part of line 2; the bracketed
-fragments appear only when their trigger holds.
+The activity state does not render as an inline glyph on line 2 — a **rail**
+carries it instead: a coloured bar in the gutter to the left of the card, the
+space nesting already reserves for indentation. The rail paints for every
+card, `Idle` included, and is independent of whatever line 2 has to say; a
+card with nothing else to report still shows its rail next to the bare
+command. `<duration>` follows in the rail's colour when shown. There is no
+state word and no second badge: the rail exists so the state is still legible
+when a row is dimmed or the terminal renders the duration in the default fg.
+
+In the **web client** the rail is a 5px bar positioned inside the row's own
+indent gutter — it shifts outward with nesting depth exactly as the gutter
+does — spanning the full card height. It carries motion, reserved for states
+that need attention (DESIGN.md's "living signals" rule): a slow breathing
+opacity while `Active`, a hard blink while `AwaitingInput`, a fast flash while
+`Error`. `Idle` is solid and still, on purpose. `prefers-reduced-motion`
+leaves every state as a solid bar.
+
+In the **TUI** the rail is a one-column-wide block glyph (`▌`) in the state's
+palette role, leading the existing indent gutter (`INDENT`/`META_INDENT`) on
+both the name row and the meta row, so the two lines read as one continuous
+bar. Folder headers gain a matching blank leading column so labels still
+align under session names. The TUI has no render cadence to animate against,
+so its rail is always static — colour is the whole signal there, as it
+always was.
+
+Either client's rail carries the accessibility duty the old inline dot did:
+it is the element whose `title`/`aria-label` names the state, so status still
+never relies on colour alone.
 
 `<duration>` renders only once the session has been held in its current
 activity state longer than **30 seconds** (`activity_since` from #102) — under
-that threshold the duration is absent and the dot renders alone. A payload
-that predates #102 (no usable `activity_since`) likewise contributes no
-duration — the dot still renders. This rule now governs only the duration
+that threshold the duration is absent and the rail carries the state alone. A
+payload that predates #102 (no usable `activity_since`) likewise contributes
+no duration — the rail still renders. This rule now governs only the duration
 fragment; it no longer decides whether line 2 exists.
 
 `<detail>` is an agent-reported string (#105) — e.g. why a session is in