chore(usage): decompose services/usage.ts into per-provider usage/* leaves (999 → 253)

[MumuTW]

Phase 1 god-file decomposition, 1 of 3. Independent of the sibling PRs — disjoint file sets, mergeable in any order.

What

open-sse/services/usage.ts 999 → 253 lines. Ten per-provider usage fetchers move into usage/* leaves (crof, nanogpt, qoder, opencode, deepseek, bailian, vertex, xiaomi-mimo, xai, github). usage.ts becomes a thin provider→fetcher dispatcher.

Behavior-preserving move. The public import surface is unchanged — usage.ts re-exports the symbols that existing tests import from services/usage (buildKiroUsageResult, discoverKiroProfileArn, parseQoderUserStatusUsage, glmMonthlyRemainingPercentage).

Faithfulness

Mechanically verified rather than eyeballed — every moved function body was extracted from both revisions and compared after normalizing comments/whitespace:

• 15 of 15 moved functions are byte-identical to their pre-move bodies
• no function lost (nothing present in the old file is absent from leaves + host)
• no function duplicated (nothing left behind in the host that also lives in a leaf)

Verification

Check	Result
typecheck:core	clean
check:cycles	no cycles
check-file-size	new leaves ≤ cap 800 (largest 230)
Pre-existing suites touching services/usage	452/452 pass
New split tests	pass

The new *-split.test.ts files are characterization tests — they lock the export surface and a couple of edge assertions, and say so in their header comments. They are not the regression guard; the 452 pre-existing tests are, and they are green.

Inherited base-red (not from this PR)

release/v3.8.49 is currently red on two gates that this branch does not touch:

• lint — stale suppression count, fixed by chore(ci): resync stale no-explicit-any suppression count for proxy-registry.test.ts #8544
• file-size — providers/page.tsx (1990 > 1927) and tokenHealthCheck.ts (843 > 841), fixed by chore(quality): ratchet file-size baseline to current code dimensions #8532 / refactor(dashboard): clear file-size base-red by extracting provider-card highlight wiring #8524

Both were verified present on the base at branch point.

[diegosouzapw]

Verified independently: diff against the merge-base matches your stated +1648/-840 across 22 files exactly, every new *-split.test.ts is additions-only (no existing test line removed), typecheck:core and check:cycles are clean, and all 364 tests across the usage-related suite pass on your branch. Confirmed the two inherited base-red gates (file-size on providers/page.tsx + tokenHealthCheck.ts, db-rules on compressionDetailNormalizers.ts) are untouched by this diff — pre-existing, not caused by this PR. Real production consumers (quotaCache.ts, providerLimits.ts, saturationSignals.ts) only ever import getUsageForProvider, which the dispatcher still exports unchanged, so nothing external breaks. This looks merge-ready — nice clean decomposition, thanks for doing the byte-level faithfulness check up front.

[MumuTW]

Rebased onto the current release tip (4053e2314). The four inherited base-red gates you confirmed are now actually fixed upstream — #8544 (ESLint suppressions, merged), #8534 (check:db-rules), #8539 (backoff assertions), #8561 (check:file-size rebaseline) — so this PR's CI should come back green on its own merits rather than needing the base-red carve-out.

Re-verified on the rebased head: the 10 usage-*-split.test.ts files pass 36/36, and check:file-size is OK (182 frozen files, no violations). Pure rebase, no content changes.

[MumuTW]

Correction to my comment above: Fast Quality Gates will still be red after the rebase, and it isn't this PR. #8561 fixed check:file-size and thereby unmasked a fifth base-red gate behind it in the same job — check:complexity-ratchets (complexity 2169 > baseline 2130, cognitiveComplexity 956 > 951).

I measured it on pristine detached checkouts with an empty working tree: 4053e2314 (current tip) and 30709255c (the base you reviewed against) both report 2169 / 956 — identical to this PR's head, so it predates #8561 and is not caused by anything here. It was hidden because check:file-size ran earlier in the same bash -e job and short-circuited it. Full measurement table in my comment on #8546.

The gate is in quality.yml's fast-gates job, so it's red for every PR against release/v3.8.49 regardless of content. Everything else on this PR is green and verified locally.

[diegosouzapw]

Thanks @MumuTW — merged into release/v3.8.49 via the local merge-train (validated as one combined tree: full test:unit + test:vitest 274/274 on the 32-core box, tip d4b9ce6016). Your commit keeps its authorship. 🚀