An open pull's page renders in under 20 ms: its `render` phase is 60–70 ms today because reads hide inside it #8389

Intent: a pull, the thing the owner reviews most, opens at once.

Measured 2026-11-02: /trevato/forge/pulls/8377 app 148–195 ms with render 52–71 ms; #8376 render 60 ms; a merged pull (#8264) render 16 ms. The page is src/web/pages/pull.ts; its render phase includes reads made while building the HTML (the step, the preview, the looks, the tells or the crew line).

Done looks like:

• [ ] Every read the page makes happens before render and is its own Server-Timing phase; render only builds HTML.
• [ ] The slowest of those reads is batched or cached so the page's total read for an open pull with a preview and looks is under 60 ms excluding diff; the pull names before/after per phase.
• [ ] A test asserts the pull page's Server-Timing names those phases and that render takes under 20 ms for a seeded open pull with checks, looks and a preview record; the existing pull page tests pass unchanged.

Files: src/web/pages/pull.ts, test/pull-page-phases.test.ts (new). Risks: the page streams; keep the first paint unchanged.