fix(trail): show project trail phase and last activity

Project trail show and list printed only the lifecycle status, so a trail whose changes had all merged read "open" in the CLI while entire.io showed it as Complete. The server sends the derived phase next to the status, but api.ProjectTrail had no field for it and dropped it on decode.

The server also no longer sends updatedAt for project trails, so --json printed the zero time. Read lastActivityAt instead, and omit it when unknown.

trail show now prints Phase after Status and Last activity instead of Updated; trail list gains a PHASE column. --json carries phase and lastActivityAt.