docs(changelog): record the July 6 evening arc

CI gate, ambiguity gate + same-day 302-to-zero burn-down, 36% smaller
browser canvas, Quaternions API adoption, sync/auth concurrency fixes,
bounded exit push, server auth hardening.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,45 @@ project follows [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- **CI workspace gate.** New `test.yml` workflow runs clippy (deny warnings)
+  and the full test suite on every master push and PR — previously no CI ran
+  tests at all. Caught its own first bug (missing Bevy native deps) on its
+  own PR. (#135)
+- **Schedule ambiguity gate.** A headless test builds the gameplay plugin
+  cluster with Bevy ambiguity detection promoted to error. The initial
+  measurement found 302 system pairs with conflicting data access and no
+  ordering; four burn-down batches (PRs #146–#149) took it to ZERO the same
+  day, and the gate now enforces 0. Keyboard consumption, board painting,
+  and HUD updates all have deterministic order for the first time.
+
+### Changed
+
+- **Browser canvas 36% smaller.** `canvas_bg.wasm` shrank 36.2 MB → 23.2 MB
+  via a size-focused `wasm-release` profile (fat LTO, single codegen unit,
+  opt-level "s"); verified visually identical in production. (#134)
+- **Quaternions API adoption.** Canonical `FOUNDATIONS`/`TABLEAUS` consts in
+  `solitaire_core` replace five scattered enum lists; upstream
+  `Suit::SUITS`/`Rank::RANKS` replace nine hand-rolled arrays, with the
+  texture-atlas indexing re-keyed through tested canonical helpers. Net
+  −177 lines. (#137)
+
+### Fixed
+
+- **Sync push race.** The server's load→merge→store cycle now runs in one
+  transaction; concurrent pushes from two devices can no longer overwrite
+  each other's merge. (#136)
+- **Refresh-token rotation is single-use under concurrency** — rotation
+  gates on the DELETE's row count, so a stolen-then-replayed refresh token
+  loses the race and gets 401. (#136)
+- **Exit sync push actually completes.** Was a detached task killed by
+  process teardown; now a bounded 2-second blocking wait on the app's final
+  frame. (#138)
+- **Server auth hardening.** Login timing no longer reveals whether a
+  username exists; concurrent duplicate registration returns 409 instead of
+  500; avatar uploads are magic-byte checked. (#144, issues #139–#141)
+
 ## [0.41.1] — 2026-07-06
 
 ### Fixed