The home's live fragments /live/apps and /live/on-you name their Server-Timing phases: session, read, render #5400

For: the home refreshes these two fragments in place (liveAppsFragment, liveOnYouFragment, src/web/studio/home.ts). When the home feels slow, they should say whether the read or the render was slow.

Done:

• [ ] Each marks session (notePhase(ctx.request, "session", takeSessionTime(ctx.request))), its read (apps and asks) with timePhase, and render.
• [ ] Their lines leave UNNAMED in test/server-timing-sweep.test.ts, and that sweep passes.
• [ ] A new test, test/live-fragments-timing.test.ts, asserts the phase names on each route and fails without the change.
• [ ] Bodies and status codes are unchanged.

Files: src/web/studio/home.ts, test/server-timing-sweep.test.ts, test/live-fragments-timing.test.ts. Why: the sweep lists these pages against #3390, which was closed as dropped, so no open issue would ever take them off.