fix(web): bound message loading and use native scroll geometry

[GenerQAQ]

Why we need this PR?

Conversation entry from Inbox, DM or threads could stay behind a skeleton or lose its target/unread position when reads, metadata or layout arrived late.

What changed

• Bound necessary reads and positioning, provide manual Retry, and preserve current account/access ownership.
• Keep bodies and decorations in one measured native coordinate system; retain target/New/Present intent and read eligibility.
• Preserve viewport resize position through qualified native/DOM handoff; scope input protection to the scroller and keep compensation readback with its existing owner.

Validation

Frozen fb560f4: normal checks/hooks and 80 scroll controls pass; local changed-line coverage is 970/970. Exact-head Hosted CI passes; complete artifact/source-checkout review is pending.

Owner original3: 2 passed, 1 failed. Normal-flow rapid-grow-two loses 142px against the original 1px contract. Independent direct34: 28 passed, 3 failed, 3 serial-skipped; it ended before the stop action. Inbox41 was cancelled. Earlier failures remain separate.

Integration with #865, account/access edge cases and native QA remain unfinished. Originals are retained. Merged at the owner's request with known failures accepted to unblock subsequent work.

Checklist

• Tests added/updated as needed
• All CI checks pass
• Browser/runtime acceptance complete
• PR targets the correct branch

Impact Areas

• Shared library (@alook/shared)
• Web app (@alook/web)
• App (@alook/app)
• Email Worker (@alook/email-worker)
• WebSocket DO (@alook/ws-do)
• CI/CD
• Other

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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