Preserve disclosure scroll contract with rapid toggles

[hamzamerzic]

Summary

• retain the disclosure-target reader-gesture guard added in Land reviewed production-local UX fixes #82
• keep Land reviewed spacer and voice production fixes #84’s rapid-toggle spacer bookkeeping and voice-dictation improvements intact
• restore the regression test that proves a disclosure tap is not treated as a reader swipe, while a real touchmove still is

Why

The #84 production transplant was applied directly to main and accidentally reverted the newer #82 guard. The WeakMap and the guard cover different races: the WeakMap unwinds a provisional spacer on a rapid later toggle; the guard prevents the initiating tap/clamp from deferring the authoritative layout pass and causing a second viewport movement.

Verification

• frontend library: 1,101 passed
• frontend hooks: 46 passed
• total frontend: 1,147 passed
• production Vite/PWA build passed
• git diff --check passed
• exact combined chat-redesign disposable-stack run in progress; full exact-head CI required before merge

[hamzamerzic]

Exact combined local runtime verification is now complete: scripts/playwright-local.sh --allow-local-e2e tests/chat-redesign.spec.mjs passed all 13 scenarios (20.7s) on f9af1b48e. Together with 1,101 lib + 46 hook tests and the production PWA build, local gates are green. Awaiting exact-head full GitHub CI before merge.

[hamzamerzic]

Closing per the direct-to-main workflow. The reviewed commit is being imported with an additional keyboard-disclosure lifecycle fix and will be pushed to main after exact combined verification.