Add native Go pricing package

[Kludex]

Adds a nested Go module at packages/go with embedded generated pricing data, model/provider matching, usage extraction, tiered and conditional pricing, and forward-compatible warnings. The shared 1,577-response dataset verifies parity with the Python and JavaScript implementations, and CI now formats, lints, race-tests, and covers the Go package.

Closes #407.

AI Disclaimer

This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.

[macroscopeapp]

Macroscope skipped reviewing this pull request. Per-review cost limit exceeded (workspace setting).

This review would cost an estimated $27.33, which exceeds your per-review limit of $10.00.

The top 3 files driving up this estimate:

File	Diff Size	Estimate
packages/go/internal/data/prices.json	464.24KB	$23.21
packages/go/data_units.go	19.94KB	$1.00
packages/go/types.go	12.19KB	$0.61

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[cubic-dev-ai]

All reported issues were addressed across 27 files

Not reviewed (too large): packages/go/internal/data/prices.json (~1 lines) - if these are generated or fixture files, add them to ignored paths to exclude them from future reviews.

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 17 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[Kludex]

@macroscope-app review please

[macroscopeapp]

Manual reviews triggered for commit 92a7cf5:

• Approvability Check
• Correctness Check

^{All prior checks · these links stay valid even if you push more commits.}

[macroscopeapp]

Review started; results will be posted as checks.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR introduces a substantial production-facing Go pricing and usage-extraction module, including new runtime logic, embedded data, and billing-related calculations, rather than a bounded maintenance change. It also modifies Macroscope configuration and has unresolved medium/high findings concerning pricing accuracy, overflow handling, provider matching, and download behavior.

Not approved because:

• automatic approval is not enabled for this workspace
• 8 blocking correctness issues found at or above your repo's Minimum Blocking Severity

^{Enable approvability here. Adjust the Minimum Blocking Severity for this repo — including turning it Off — in Settings. You can add or adjust custom eligibility rules. Learn more.}

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 8 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>