docs(t3x): re-baseline the seam ledger against the follow-up merge-base

The 2026-08-08 sync ran in two passes. This is the second: four more
upstream commits (usage page pingdotgg#5684 + chart fix pingdotgg#5697, mobile settings
sheet pingdotgg#5625, desktop zoom-shortcut fix pingdotgg#5691), merge-base a20923c.

Only two rows moved on the file-list half. ThreadComposer.tsx went
+26/-4 to +27/-4 because pingdotgg#5625 rewrote the file around the fork's edit
and the resolution re-attaches the line-break button to upstream's new
single settings trigger. pnpm-lock.yaml went +196/-143 to +317/-737,
which is PR #63's repair showing up rather than new churn.

That second number is the reason the lockfile note grew a paragraph.
The first pass resolved all three lock conflicts with --ours and ran
pnpm install --lockfile-only, which preserves any existing pin that
still satisfies the semver range instead of floating to the newest --
so seeding from upstream's lock silently discarded the security sweep
and reopened 21 Dependabot alerts. The overrides: block survived
byte-identical and did not save it. Seed from the fork's pre-sync lock.

Churn and risk are regenerated in the same commit, so both halves of
the ledger agree on one merge-base. server.ts churn 32 to 33.

Author: radroid