v0.4.0 — multiplayer Phases 0 and 1: seat and player split apart, turn state per player, the page behind a Session, and eight seat/player mix-ups fixed with tests that fail without them

CHANGELOG.md

@@ -21,6 +21,85 @@ page as `v0.1.0 · <sha> · <date>`, so what is deployed can always be identifie
 
 ## Unreleased
 
+## 0.4.0 — 2026-08-13
+
+### Phases 0 and 1 of the multiplayer plan — the seams, not the server
+
+`docs/architecture/multiplayer.md` is the plan; this is its first two phases. Nothing a player can see
+changed, and that is the exit criterion: the whole point is that solitaire is byte-for-byte the same
+game while the code underneath it stops assuming there is only ever one of you.
+
+**Seat and player are now different things.** They were the same integer everywhere, which is correct
+today and wrong the moment Employee Rotation moves someone to a different chair. Offices and districts
+are keyed by SEAT; hands, Revenue and the Fedora belong to the PLAYER. `seating[]`, `seatOf` and
+`playerAtSeat` make the mapping explicit — it is still the identity mapping, so nothing moves yet.
+
+The split immediately found a real bug: `awardDeparture` was indexing `s.players` with a seat. Correct
+under the identity mapping, silently paying the wrong railroad under rotation, and unfalsifiable in
+solitaire. That is what the change is for.
+
+**Per-player turn state.** `turn: TurnState` became `turns: Map<PlayerIndex, TurnState>`, one per
+player at phase entry, read through `turnOf(s, player)` at ~50 sites. **Behaviour-neutral by
+construction** — the phase cursor still walks one player at a time, and every existing test passed
+unchanged. It is done now rather than in Phase 2 because it is a wide, mechanical change to the engine
+that costs almost nothing today and would be a rewrite once a wire format depends on the shape. What
+it buys later is players acting in parallel where the rules allow it, which is where the latency in a
+turn-based game over the internet actually lives.
+
+**The page renders from `Frame` + `Menu` alone.** `main.ts` had eleven reads through into `GameState`
+— the deck, the RNG, other players' hands — each one a thing a server would never send. `Frame` grew
+`option`, `status`, `outcome`, `players[]` and `handCount` to cover them. A test now reads `main.ts`
+and fails if a reader comes back, because the cheap moment to catch that is now and not in Phase 2.
+
+**A `Session` between the page and the game.** `LocalSession` runs the engine in the browser exactly
+as before; a `RemoteSession` will hold no authoritative state at all — it cannot, having neither the
+deck order nor the other hands. So the interface is deliberately the smaller of the two, and what only
+a local session can do (undo, local save, dealing a new game) is declared in `capabilities`, which the
+page reads to hide those controls rather than calling them and failing. `submit` is async even though
+the local one answers immediately: a page written against a synchronous submit would have to be
+rewritten for the server.
+
+`test/session.test.ts` is the proof — 13 tests, the first of which plays seed 77 to a finish through
+both routes and asserts the boards and the histories are identical.
+
+**Docs.** `protocol.md` was written from the rules before the engine existed and had become a second,
+drifting copy of `intents.ts` and `events.ts`; it now points at them and keeps only what the types
+cannot say — what is deliberately *not* an intent, the two loops a client must not flatten, and the
+redaction surface. Three architecture documents still said WebSocket where D5 chose SSE + POST; fixed.
+
+**Then a review found the seat/player audit was half done, and it was right.** Two flagged sites, and
+sweeping for the pattern found six more. All of them are correct today and all of them break the
+moment Employee Rotation lands, which is exactly the failure mode the split was supposed to end.
+
+*Keyed an Office Area by player when `officeAreas` is keyed by seat:* `refusesThisOffice`
+(`apply.ts` — the Crack Limited's terminals-only rule), `spendDispatchBonus` (`advance.ts` — the
+Fedora is held by a PLAYER, the Telegraph is installed in a SEAT), `impediments` (`narrate.ts`), and
+two district lookups in the bot. `adTrackCount(s, player)` in `narrate.ts` was passing a player into
+a `SeatIndex` parameter — the type said seat and the caller said player, and TypeScript cannot tell
+two `number` aliases apart, which is precisely why this needs a test rather than a type.
+
+*Read seat 0 regardless of the viewer:* the bot's `takingRank` ranked a face-up Office card against
+**seat 0's** Office tier for every player, so in a multi-player bot game everyone chased player 0's
+upgrade. `stats.ts` and `save-replay.ts` also index seat 0, which is correct — they are solitaire
+summaries — and now say so through `areaAtSeat` instead of looking like the same bug.
+
+**And `Frame` was seat-scoped in the board and the hand but not in four fields beside them.**
+`revenue`, `moves`, `blocked` and the pace note all still reported player 0. A player would have been
+shown someone else's score, someone else's Moves remaining, and someone else's jammed facilities —
+that last one a list of squares that are not on the board they are looking at. Worse, the crew lookup
+was keyed by `row,col` alone while every district shares an origin, so a crew standing at (0, 1) in
+one Office Area was drawn at (0, 1) on **every** player's board.
+
+Five new tests, all of which fail against the previous commit: per-seat Revenue/pace/impediments,
+crews staying on their own board, a full 3-player game played with `seating` rotated before the first
+move, impediments following a player to their new chair, and a source-level guard that fails if
+anything outside `state.ts`/`apply.ts` touches `officeAreas` directly — the class, rather than the
+eight instances of it found by hand.
+
+Bot unchanged at 7.0 mean over 200 solitaire Standard games (the bot fixes are behaviour-neutral with
+one player), and all four published replays still play to the end — which, for a change of this width,
+is the whole report.
+
 ## 0.3.1 — 2026-08-13
 
 ### Groundwork for multiplayer