Fleet page: measure the four facts, problems and badge as defined

[Jacksondr5]

The Fleet page exists (#149, #241, #242, #244) and merges every connected environment, but it falls short of docs/j5/product/features/fleet-page.md:

• no command-palette entry (AC4);
• status reuses the sidebar pill: no Failed, no "Waiting to start · Nm", "Idle" without a time, and upstream's "Completed" shows (AC15, AC16);
• open asks are a single owed count, with no Awaiting count or hover list (AC18);
• last activity is an unlabeled updatedAt age (AC19), and ? has no reason on hover (AC20);
• no failed-run, delivery-alarm or dispatch-threshold problems (AC21, AC22, AC24);
• the badge counts agents owing a reply, which AC23 excludes;
• no footer for threads without a home (AC13), and the header names neither the environment nor an as-of time (AC25).

Supersedes #28, whose body describes the dropped one-Squadron-at-a-time page.

Carried over from the dogfood v0 plan's "what the current build narrows" table, which #354 removes.