refactor(ui): converge remaining sidebar row indicator sizes #743

Context

Follow-up to #738.

The session-row overflow menu introduced by #738 is already converged onto the shared Base UI Menu primitive. Menu-open state, popup sizing, offsets, and destructive colors are handled in #738.

This issue tracks pre-existing size literals in the surrounding sidebar row CSS.

Scope

Audit and converge:

• .maka-list-row-streaming-dot: 8px
• .maka-list-row-unread: 8px
• .maka-list-row-text: 24px
• .maka-list-row-status-icon: 14px

Prefer existing tokens where semantics already match:

• 8px → var(--space-2) or a shared indicator-size token
• 24px → var(--h-control-sm)
• Evaluate whether the dense 14px status icon should remain an explicit exception or converge to var(--icon-size) without degrading row density

Also evaluate whether streaming and unread indicators should share a small CSS primitive instead of duplicating geometry and halo declarations.

Non-goals

• Session-row overflow menu behavior
• Menu popup sizing or positioning
• Destructive menu colors
• Broader sidebar/navigation redesign
• Mechanical replacement of every numeric CSS value

Acceptance criteria

• No unexplained 8px, 14px, or 24px geometry remains in the audited session-row indicator path
• Any retained exception is documented and covered by a governance test
• Streaming, unread, stale, active, and reduced-motion states remain visually correct
• Verified at 1280px and 990px Electron viewport variants
• Relevant computed-style/token contracts pass