Add The Frontier, a second setting, and a picker to choose between them

Cold Fork is a freight yard: 29 events across two stages, a four-day cycle, and
its own relationship and skill vocabulary. src/engine/ was not touched. Adding it
needed three changes outside the engine: one save slot per pack, app.js holding
the current pack, and turn.js no longer naming the mailroom (DECISIONS #34).
build.js now handles imports wrapped across lines. A conformance suite runs over
every registered pack. DECISIONS #35 records three calls on open questions.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RxdJFbLq1rBKsUeticGV1g

README.md

@@ -9,13 +9,14 @@ retrospective.
 
 The engine knows nothing about offices, mailrooms or bosses. A **setting is a
 content pack** — characters, events, choices, stat names and tuning, all data.
-`corporateladder` is the default pack; a Wild West or lemonade-stand pack would
-be new data and no new code.
+Two ship: **Corporate Ladder**, a modern office and a mailroom, and **The
+Frontier**, a freight yard at the end of a stage line. They share every line of
+engine code and no content at all.
 
 ## Status
 
-Engine and the first content pack are built and tested. No UI yet — the game is
-currently playable only from a test harness.
+Engine, interface and two content packs, all built and tested, and played in a
+real browser.
 
 | Piece | State |
 | --- | --- |
@@ -33,7 +34,10 @@ currently playable only from a test harness.
 | Repetition analytics (`npm run analyze`) | done |
 | Version and build shown on screen | done |
 | Keyboard play (Enter / Tab) | done |
-| Played in a real browser | done — first playtest 2026-09-09 |
+| Second content pack — The Frontier, 29 events, two tiers | done |
+| Setting picker, one save slot per pack | done |
+| Pack conformance suite (every pack, every check) | done |
+| Played in a real browser | Corporate Ladder yes, first playtest 2026-09-09; **The Frontier not yet** |
 
 The first playtest confirmed the interface, saves and the exported log all work
 in a real browser. Its findings — an unexplained daily drain, no sense of the
@@ -70,9 +74,16 @@ That is one self-contained file with the stylesheet and every module inlined.
 It plays by double-clicking it — no server, no network, nothing installed.
 
 ```sh
-npm test          # 121 tests: engine, content, UI wiring, and the build
+npm test          # 149 tests: engine, both packs, UI wiring, and the build
 ```
 
+Tests are in three layers. `test/conformance.test.js` runs over **every pack in
+the registry** and asserts only what is true of a pack because it is a pack —
+validity, no dead content, the declared economic baseline, variety, replay from
+seed, a way out of every event. `test/content.test.js` and
+`test/frontier.test.js` hold each pack to its own tuning. The engine suite runs
+against a fixture pack, so tuning a setting can never break it.
+
 To see what a playtest actually did — turns against distinct situations, how
 often each recurred, which locked gates players kept meeting, and anything they
 typed into the feedback box:
@@ -90,26 +101,32 @@ used only to run the tests, the single-file build, and the log analyser.
 
 ## Where things stand
 
-The MVP is complete and has survived three playtests. Two tiers, 31 events, a
-retrospective, saves, and a feedback log that has already found one real bug.
+The MVP is complete and has survived three playtests, and a second setting now
+exists to prove the engine/content split holds. Adding it required **no engine
+change** — and three interface changes, two of which were latent defects a
+second pack made visible (a single global save slot, and the one place the UI
+still named a setting). See DECISIONS.md #34.
 
 Open questions, in the order they are likely to matter:
 
-- **Does money stop mattering late?** A careful player ends around $8,300 over
-  200 turns. Tuning has been corrected twice from playtest logs and should be
-  judged from a session, not from simulated play — that is how the last trap got
-  in.
-- **`skills.negotiation >= 15` gates four different early options.** The logs
-  show players bouncing off it repeatedly in the first thirty turns. It is
-  probably set too high for how slowly the skill grows.
-- **Nobody uses the feedback widget.** Zero ratings across three sessions. The
-  locked-gate data in the log has been more useful than anything typed; the
-  widget may need to be more present, or may not need to exist.
+- **The Frontier has never been played by a human.** Its economy is asserted by
+  the conformance suite and exercised by six archetypes, and that is exactly the
+  evidence that was not enough the last two times. It needs a session before its
+  numbers are believed.
+
+- **Money stops mattering late, and it should not.** A careful player ends
+  around $8,300 over 200 turns. The direction is set: standing should cost
+  money to keep — a better car, a better place to live, better clothes — so
+  expenses climb as the player rises. Not built yet.
 - **Dispatch is eleven events against the mailroom's nineteen.** It passes the
-  variety guard, but it has had far less play than the mailroom.
-- **The third tier, or the second content pack.** Promotion working entirely as
-  data is decent evidence the engine/content split holds; a second *setting*
-  would be the proof.
+  variety guard, but it has had far less play than the mailroom. Waits on more
+  playtesting.
+- **A third tier in either pack.** Two rungs is what both settings have. The
+  split is now proven across settings; it is not proven across a long ladder.
+  Waits until the Frontier has been played.
+
+Settled, and not open: Corporate Ladder's negotiation gate stays as it is, and
+the feedback widget stays as it is (DECISIONS #35).
 
 ## Layout
 
@@ -124,13 +141,16 @@ src/engine/     the game engine — imports nothing from content/, or from src/u
   rng.js          seeded, serializable RNG
   validate.js     load-time content checking
 src/ui/         screens, formatting and the app controller
-  app.js          the only module that names a content pack
-  screens/        the turn screen and the retrospective
+  app.js          the only module that knows there is more than one pack
+  screens/        the turn screen, the retrospective, the setting picker
   format.js       state paths and conditions rendered as English
-src/io/         local-storage save, file export/import, the feedback log
-content/        content packs (settings)
+src/io/         local-storage save (one slot per pack), export/import, feedback log
+content/
+  index.js        the pack registry — the only list of settings
+  corporateladder/  a modern office and a mailroom
+  frontier/         a freight yard at the end of a stage line
 tools/build.js  flattens everything into one self-contained HTML file
-test/           engine tests against a fixture pack; content and UI tests
+test/           engine tests against a fixture pack; conformance, per-pack, UI
 docs/           DECISIONS.md — why things are the way they are
 Planning/       the original design documents
 ```