docs: update merged-work lessons (2026-10-20 → 2026-10-21)

[e54-bot]

Summary

Nightly merged-pr-retro sweep of merged PRs 2026-10-20 → 2026-10-21 adds four failure classes:

• Unconditional async writes overwrite newer state — load() erased a selection made while rules loaded (feat(ui): structured read-only Workshop rule view #829, fixed by fix(ui): keep the selected rule and wait for the initial load in E2E #863), and the fix's first cut wrote warmedFor unconditionally (fix(ui): keep the selected rule and wait for the initial load in E2E #863 round-1 review finding). Two incidents in a three-day window; escalated as wright#868.
• Connection: close drops in-flight client work — wright ui advertised close on every response; pipelined POSTs hung (feat(cli): add wright ui command and loopback endpoint #827, fixed by fix(ui): keep connections alive in wright ui #864).
• E2E asserted on state it did not await — fixed 15 s window and reads before content flushed; waits landed in fix(ui): keep the selected rule and wait for the initial load in E2E #863, CI gate removed in ci: stop running the UI browser E2E in CI #865.
• Dependency bumps re-audit the footprint — jsonschema 0.58 default features pulled in ~262 lock entries (chore(deps): bump jsonschema from 0.18.3 to 0.58.6 #866 review finding, fixed with default-features = false).

Docs-only change to docs/LESSONS.md.