feat(usage): add hotdata usage command

[eddietejeda]

Summary

SDK 0.4.0 (#171) added the usage API (GET /v1/usage), but the CLI exposed no command for it. This adds hotdata usage:

hotdata usage [--since <rfc3339>] [--workspace-id <ws>] [--output table|json|yaml]

Reports workspace usage for the current billing window (or since --since): query_count, bytes_scanned, storage_bytes, and storage_captured_at.

Behavior

• query_count and bytes_scanned accrue per query in real time (data reads).
• storage_bytes is a periodic snapshot taken at storage_captured_at, so uploads are reflected on the next capture, not instantly.
• Table view renders byte counts human-readably (e.g. 21.7 MiB (22706766 B)); -o json/yaml keep raw integers.

Implementation

• New src/usage.rs, wired through command.rs + main.rs.
• Uses the seam's raw get_json("/usage", …) helper — there's no typed SDK handle for usage (only the free usage_api::get_usage function), and this matches how indexes.rs already does untyped GETs.
• Output shape is a curated struct (decoupled from the generated model), consistent with databases/indexes.
• Documented in the core hotdata skill (subcommand list + a Usage section).

Tests / verification

• Unit tests: response deserialization (incl. null storage_captured_at) and the human-bytes formatter.
• Full suite green (211 passed); fmt/clippy clean for the new code.
• Verified against production (AgentRyan):
  • hotdata usage → table with all five metrics
  • hotdata usage --since 2026-06-15T00:00:00Z -o json → query_count drops from 186 (month-to-date) to 45, confirming --since is honored

[claude]

LGTM. New usage command follows existing conventions (untyped get_json seam like indexes.rs, curated output struct, table::print). Well-tested: unit scaling, exact-value preservation, and null storage_captured_at.

[codecov]

Codecov Report

❌ Patch coverage is 55.55556% with 28 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/usage.rs	62.50%	21 Missing ⚠️
src/main.rs	0.00%	7 Missing ⚠️

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