[deep-report] [Code Quality] Unify token-usage metrics quartet and fix camelCase/snake_case json-tag inconsistency

[github-actions]

Description

The token-usage metrics quartet {InputTokens, OutputTokens, CacheReadTokens, CacheWriteTokens} (plus Effective/Reasoning) is modeled four times, with an inconsistency worth fixing during consolidation:

• pkg/cli/copilot_events_jsonl.go:100 — copilotUsageMetrics (uses camelCase json tags)
• pkg/cli/token_usage.go:75 — ModelTokenUsage (snake_case json tags)
• pkg/cli/token_usage.go:90 — ModelTokenUsageRow (a flattened near-dup of ModelTokenUsage)
• pkg/cli/token_usage.go:27 — TokenUsageEntry

Extract a shared token-metrics core struct and embed it, aligning the json tag casing (the camelCase vs snake_case split is a latent serialization footgun).

Expected Impact

Single source of truth for token metrics, removes the camelCase/snake_case json-tag inconsistency, and collapses the ModelTokenUsage/ModelTokenUsageRow near-dup.

Suggested Agent

Code Quality agent (Go refactor). Typist audit context available.

Estimated Effort

Medium (1-4 hours)

Data Source

DeepReport Intelligence Briefing 2026-07-16, from the [typist] Go Type Consistency report (Cluster 8). Clusters 1/2/3/6 were already filed (#46000/#46001/#46002); Cluster 8 was un-filed as of this run.

Generated by 🔬 Deep Report · 247.5 AIC · ⌖ 12.4 AIC · ⊞ 10K · ◷

• expires on Jul 18, 2026, 7:30 AM UTC-08:00

[github-actions]

🍪 Issue Monster selected this for Copilot

I've identified this issue as a good candidate for automated resolution and requested assignment to the Copilot coding agent.

If assignment succeeds, the Copilot coding agent will analyze the issue and create a pull request with the fix.

Om nom nom! 🍪

🍪 Om nom nom by Issue Monster · 2.93 AIC · ⌖ 5.93 AIC · ⊞ 7.6K · ◷