Release 0.3.2: decode Grok zero usage correctly

[thrr87]

Grok omits creditUsagePercent at zero usage. Version 0.3.1 treated that as unavailable, so the user's usage display remained broken after reset.

Decode an omitted percentage as 0% used / 100% remaining only after validating the current weekly/monthly period. The official grok.com protobuf descriptor defines an implicit-presence proto3 float; this is a protocol default, not an estimated value. Explicit null/malformed values and invalid configurations/periods still fail validation. Existing 0.3.1 partial caches trigger a fresh read on demand instead of delaying it for ten minutes; their historical data is not rewritten. Prepare version 0.3.2 (build 12).

Evidence and validation:

• Independently extracted and checked the official provider descriptor; pinned schema evidence and hashes are in docs/research/grok-zero-usage-2026-09-16.md.
• Live installed Grok Build 1.0.30: the released decoder reproduced unavailable usage; the corrected production collector returned 100% remaining and passed cache round trip, without any model request or credential access.
• Decoder and cache-delay regressions failed before their respective fixes.
• Full Release suite: 647 tests, zero failures. Final head 4f85569fdb7db5b80f57e308f28ae21aabd5d30b also passed GitHub CI and Swift/Actions CodeQL. Covers weekly/monthly omitted zero, reset/history/overview, relaunch, subsequent 1% usage, and immediate recovery from a fresh partial cache.
• Isolated signed native QA, seeded from the installed 0.3.1 cache/history: All and Grok detail show 100%, current reset and a current-window chart point. No forecast is invented from the single observation. Visible product copy checked; QA profile removed and installed app/data unchanged.
• Independent spec and standards reviews found no actionable findings; release-validator self-test passed.

Release authorization (2026-09-16): the owner explicitly approved publication of 0.3.2 after green tests and CodeQL, renewed the unperformed all-enabled idle comparison and eight-hour lifecycle soak exceptions specifically for 0.3.2, and authorized administrative merge of PR #75 without a second/code-owner approval. ADR-0015 and the PRD record that approval. Signed release artifacts must still be verified before publication.