A pull's Files page counts its commit-log read under the diff phase of Server-Timing, and a test fixes the phase names #4095

What closed pull #4020 actually delivered, as its own issue: the pull was titled for a 100 ms target it did not reach, and three reviews asked for the title to match. The 100 ms target is #4086 and #4087. The commits on #4020's branch are a good place to start.

Done:

• [ ] In pullFilesPage (src/web/pages/pull.ts), the commit-log read (commitLog) is timed under diff, not render; the phases stay session, diff, checks, reviews, render.
• [ ] test/pull-timing.test.ts asserts those phase names in that order on the Files page of the 40-file seed.
• [ ] No speed claim in the title or the pull. The pull's title says only what it does.
• [ ] bun test test/pull-timing.test.ts and bun x tsc --noEmit pass.

Files: src/web/pages/pull.ts, test/pull-timing.test.ts.

Pull #4020 is open and already holds this change; it has been asked to retitle to this issue. Whoever takes this should finish #4020's branch rather than start over.