Feature: persisted ingest, balanced, and compact compression profiles

[awksedgreep]

Parent: #28. Depends on measured profile selection.

Summary

Implement a persisted public contract for the three tested compression profiles and bounded transitions between them.

Contract

• Tables accept an explicit compression_profile='ingest|balanced|compact' creation policy.
• Existing tables retain their recorded policy on reopen.
• Public capabilities/stats expose requested profile, effective plan, encoder generation, block target, effort level, optimizer policy, pending unsettled work, and relevant resource bounds.
• A profile change affects new work immediately but rewrites existing blocks only through explicit bounded optimization.
• Unknown profiles and unsupported effective plans fail clearly.
• Readers decode every supported codec regardless of the local write profile.

Transition semantics

• Profile changes are transactional, idempotent, and rollback-safe.
• No configuration statement launches an unbounded rewrite.
• Mixed-profile/mixed-codec stores remain exact while converging.
• Downgrades state whether existing compact blocks remain or require an explicit rewrite.

Acceptance criteria

• Create, reopen, change, rollback, bounded convergence, backup, restore, and compatibility tests.
• Complete server configuration and operational documentation.
• Existing tables preserve the current behavior unless a separately reviewed default migration is approved.