Feature/Fix: Diagnose Codex reset-epoch token collisions

[iam-brain]

Summary

• add a pure, shadow-only analyzer for exact token snapshots repeated after strong cumulative-counter resets
• separate same-document reset evidence from speculative cross-owner fork collisions
• report only aggregate counts and UTC token estimates; the analyzer cannot emit accounting rows, cache data, or selector input
• add an opt-in frozen-history replay that keeps private paths, rollout identities, models, and account totals out of output

Real-world result

This does not explain the remaining July 9 undercount. The frozen corpus produced zero reset-epoch candidate tokens on July 9.

Across the wider replay, 97 same-document repeats represented about 16.3M counterfactual tokens: roughly 7.3M on July 10 and 6.2M on July 11. Cross-owner detection produced 96,008 candidates and a clearly implausible estimate dominated by copied fork history, confirming that it is diagnostic evidence rather than a safe accounting rule.

Selected totals remain unchanged.

Tests

• focused reset/shadow/local-validation suites (9 tests passed after review fixes)
• make check
• opt-in frozen replay over 819,779 observations
• make test (648 selections in 54 groups; one group timed out under concurrent SwiftPM contention and all 12 isolated selections recovered; command passed)

Closes #40. Stacked on #38.