fix(maestro): pin activity rail to left edge, drop active-state pulse

Rail now spans full row height flush to the left edge with square
corners, instead of a depth-shifted inset bar. Active state stays
solid green since colour alone already signals it; blink/flash stay
for awaiting-input/error.

docs/SIDEBAR.md

@@ -51,13 +51,15 @@ 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 **web client** the rail is a 5px bar pinned to the row's own left
+edge, square corners, spanning the full card height edge to edge — it
+shifts outward with nesting depth along with the row's own padding, since
+it is positioned relative to the row. It carries motion only for states that
+need attention (DESIGN.md's "living signals" rule): a hard blink while
+`AwaitingInput`, a fast flash while `Error`. `Active` and `Idle` are both
+solid and still — colour alone (green vs. the idle grey) is the signal for
+`Active`, so it does not also pulse. `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