chore: cargo fmt across workspace; add analytics domain to CSP

- Apply cargo fmt to solitaire_engine, solitaire_server formatting.
- solitaire_server/src/lib.rs: add https://analytics.aleshym.co to
  script-src, img-src, and connect-src so the analytics beacon loads
  without a CSP violation.
- docs and README updates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/card-game-integration.md

@@ -101,6 +101,11 @@ Our 767-line `solitaire_core::solver` reimplements the full game rules to run th
 ### 5. JSON Serialisation / Persistence
 `solitaire_core::GameState` serialises the full mid-game state to JSON via `serde` so the engine can save on exit and restore on launch. `KlondikeState` derives `Clone` + `Eq` + `Hash` but not `Serialize` / `Deserialize`. No upstream changes are needed — this is handled externally.
 
+**Current verification (2026-06-01):** `klondike v0.3.0` and `card_game v0.4.0`
+crate manifests expose no `serde` dependency/feature, and source exports no
+serde derives for instruction/state snapshot types. Keep Ferrous'
+`SavedInstruction` bridge in place.
+
 **Session history:** `StateSnapshot<G>` stores the pre-move game state and instruction. On load, the session is reconstructed from the serialised snapshot history — no full replay from seed needed.
 
 **In our wrapper:** Serialise the `solitaire_core` wrapper struct using newtypes. Define `SavedInstruction` (a `Serialize + Deserialize` mirror of `KlondikeInstruction`) and `SavedStateSnapshot`. Reconstruct `SessionState` from the deserialised history. Schema version field lives on our wrapper.
@@ -147,6 +152,29 @@ Steps in dependency order. Upstream issues #10, #11, and the solver are all merg
 
 ---
 
+## Quaternions Upgrade Runbook
+
+Use this sequence whenever upgrading `klondike` / `card_game` from the
+Quaternions registry:
+
+1. Review upstream changes/releases:
+   - <https://git.aleshym.co/Quaternions/card_game>
+   - <https://git.aleshym.co/Quaternions/klondike>
+2. Run:
+   ```bash
+   scripts/update_quaternions_deps.sh <klondike_version> <card_game_version>
+   ```
+3. If the script passes, inspect the resulting `Cargo.lock` diff and land the
+   upgrade with the normal PR flow.
+
+The script enforces:
+- lockfile update to requested versions
+- `cargo test --workspace`
+- `cargo clippy --workspace -- -D warnings`
+- deterministic replay/debug-API smoke tests in `solitaire_wasm`
+
+---
+
 ## What Does NOT Need to Change
 
 - The `solitaire_engine` Bevy layer — it works against `solitaire_core` types; changes are isolated to `solitaire_core`.