Feature/Fix: Adapt rollout snapshots for lineage accounting

[iam-brain]

Summary

Adds the first scanner adapter for the planned lineage-ledger rearchitecture. The existing fast, cancellation-aware JSONL scan now produces raw complete token observations alongside its legacy cumulative snapshots, then adapts that parsed evidence into CodexLineageLedger.Document values.

This is a stacked PR on top of the shadow ledger foundation. It does not run the ledger from production discovery and does not change published totals.

Details

• Reuses one CostUsageJsonl pass; no second rollout parser
• Preserves canonical filename ownership, metadata session identity, and fork-parent identity
• Preserves complete raw (last_token_usage, total_token_usage) observations
• Keeps incomplete states available to the legacy snapshot path while excluding them from the ledger contract
• Propagates cancellation
• Leaves malformed timestamp policy to the mapped conservative-evidence slice

Validation

• swift test --filter CodexLineageLedgerTests — 9 tests passed
• make check
• SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.5.sdk make test — all 639 selections passed across 54 groups with no retries or timeouts
• Repository review gate: no material findings

Tracks Feed the fast parser into typed rollout documents.