feat: add Oh My Pi and Grok Build collectors

[Tab-ome]

Summary

• add an Oh My Pi collector for exact assistant-message usage under ~/.omp/agent/sessions, including nested subagent transcripts
• add a Grok Build collector for completed-turn usage under ~/.grok/sessions, with cache normalization, per-model attribution, API call counts, and server-reported cost conversion at 1e10 ticks per USD
• handle very large Grok JSONL events without a fixed Scanner token limit
• expose both sources in config, Docker examples, dashboard filters, and bilingual documentation

Accounting semantics

• OMP input, cache read, cache write, output, and reasoning fields map directly to the repositories non-overlapping token model
• Grok inputTokens includes cached input, so non-cached input is clamped after subtracting cachedReadTokens and cacheCreationTokens
• incomplete or partial Grok costs are not trusted; normal pricing fallback remains available
• source-prefixed session IDs and source-scoped dedup keys avoid collisions with Pi and other collectors

Validation

• go test ./...
• go vet ./...
• git diff --check
• real-format smoke scan against local OMP and Grok Build session trees
• Linux ARM64 static build and Docker runtime version smoke