fix(fast-inbox): preserve proposals across bucket repartitioning

[spalladino]

Summary

• interpret a block proposal's Inbox reference as the rolling hash at its signed consumed-message count, so content-valid proposals survive bucket repartitioning
• read proposal bundles by leaf-count range, retry stale validator views through the attestation deadline, and re-confirm the prefix after the range read
• validate the signed prefix atomically with archiver block insertion and prune proposed blocks only when their consumed content changes
• make selector, normal sequencer, automine, validator, simulator, and final checkpoint endpoint guards consistently count-and-hash based

Testing

• yarn build
• yarn format
• validator-client focused suites: 172 passed
• stdlib archiver API suite: 63 passed
• archiver focused suites: Jest reported 189 passed; the surrounding runner exited 129 after completion
• sequencer selector suite passed; the remaining focused sequencer command was stopped at the user's request
• e2e tests not run

Stack

Stacked on #25408.

Fixes A-1925.