Fix indeterminate oplog writes and batch persistence

[vigoo]

Summary

• classify indexed-storage write failures so primary oplog retries distinguish safe transient failures, indeterminate outcomes, conflicts, and permanent errors
• reconcile a possibly committed append by reading back the expected range and accepting only an exact ID and serialized-byte match
• serialize oplog batches once and reuse the same Arc<[(u64, Bytes)]> across retries and reconciliation
• remove PostgreSQL per-row namespace/key allocations and add transactional, zero-explicit-copy SQLite batch writes with single-lookup MultiSqlite routing
• cover initial and batched appends, conflict safety, partial/different read-back, backend error classification, atomic SQLite batches, and per-agent MultiSqlite routing

Verification

• cargo fmt -p golem-worker-executor -- --check
• cargo check -p golem-worker-executor --all-targets
• cargo clippy -p golem-worker-executor --all-targets --no-deps -- -D warnings
• 19 focused golem-worker-executor tests covering GOL-535 and GOL-480
• git diff --check

Resolves GOL-535

Resolves GOL-480

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