R1:0402a79e0e57

Render object remarkup references in a text context as "Dxxx <uri>"

Summary:
Depends on D19031. Fixes T11389. Currently, we render `Dxxx` in a text context (plain text email) as just a URI.

Instead, render it like `Dxxx <uri>`. This is more faithful to the original intent and preserves `T123/T456` as two separate, usable links.

Test Plan: Wrote `T123/T234` in a task, pulled mail for it with `bin/mail show-outbound`, saw separate clickable links.

Maniphest Tasks: T11389

Differential Revision: https…