docs: traps.md — the bugs that passed a green suite

Six bugs this project shipped into a branch, what let each through, and the
guard that now catches it. They share a shape: the test passed, and the test
was wrong.

- a regression test that constructed its own correct object, so reverting the
  bug left the suite green
- GDScript default params turning an arity change into a silent miscompile,
  invisible to a grep for the renamed field (grep cannot see positional args)
- a determinism test comparing two runs that would change together
- a closed move vocabulary that was not bounded, because the model could repeat
  a tag and choose an amount in unary
- a roster written down in four places with only one pair guarded — including a
  shipped authoring skill that would have emitted origins allowing zero callings
- generated content that has a client consumer

Linked from CLAUDE.md §18 and docs/README.md. Also records M4-a on the roadmap
with its live end-to-end proof.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QYa9u7Kdxv5gX4AnwWexy8

docs/roadmap.md

@@ -75,6 +75,7 @@ Each screen is recreated as a Godot 4.7 Control-node scene against the mockups (
 
 ### M4 — Character creation
 *Content it consumes → [BOM](../content/roadmap.md#2-bill-of-materials): calling blurbs + the Bloodsworn's patron choice (fixed); origins (variable). **~4 pieces.***
+- ✅ **Creation model (M4-a)** — the rules a character is made of, no UI ([spec](superpowers/specs/2026-07-12-creation-model-design.md)). Race/calling/skill **mechanics** are static tables in code (`client/scripts/rules/`); their **blurbs** are hand-written content (`content/world/{callings,races}/`, loaded by `ContentDB`, parity-tested), so the content BOM does not block the engine. `CharacterSheet` **stores only what was rolled or chosen** (attributes, race, calling, skills, current hp/mp) and **derives** the rest (`max_hp`, `ac`, `save`, `skill_bonus`, `spell_dc`) — so no derived number can drift from its inputs, and M5's level curve is a function change rather than a stored-field migration. **`NewGame.construct` carries a seed, not a stat block:** it rebuilds the RNG and rolls the attributes itself, so it never trusts a number handed to it (§2), and the same seed yields an identical character, hidden Luck included (§10) — pinned by a golden-vector test. The roll is **3d6 with a hard floor of 8** (straight 3d6 puts ~9% on a primary the +3 pool cannot rescue; a character bad at the one thing he is *for* is the "fine" §7 forbids). **LCK is unspendable, not merely hidden.** Open seams marked honestly: `ac()` is `10 + DEX` until armor exists (M7), `max_mp()` is a `TUNABLE` placeholder (M5 owns the curve), L1 talents are id stubs (M5). **Live-proven end-to-end** (2026-07-12): a beastfolk cutpurse built by the pipeline → canon log → schema validation → `Player: Vexcca, a beastfolk cutpurse` in the digest (no numeric Luck, no stats, no snake_case id) → real narration from qwen3.5. 250 client tests, 76 api (live layer included). *§2: state · goal: the character exists in code.*
 - ✅ **Contract migration** — the two contract migrations this milestone owed have **landed**: the canon log's `player` block is now `{name, race_id, calling_id, luck_descriptor}` (the Narrator/NPCs describe the player as e.g. "a beastfolk cutpurse"), and an origin's build-constraints key is now `allowed_callings` (`content/origins/deserter.json` lists all seven real calling ids; the pre-migration key and its two dead class ids are gone from the codebase). Schemas, docs, fixtures, and the world-building skill's content template all agree.
 - ○ **Character creation UI (M4-b)** — the mock's screen over our proven model: race + calling cards, six stats with **LCK hidden entirely** (§7), 3d6 floors, the **+3 additive-only spend-up** pool (§8, matches the `character-creation-stats` model), live origin blurb + nameplate. **The class-name reconcile is settled** — all seven callings are named (Sellsword · **Reaver** · Cutpurse · Trapper · Hedge-Mage · Bonesetter · **Bloodsworn**; [races/classes spec](superpowers/specs/2026-07-11-races-and-classes-design.md) §4). Feeds new-game canon-log construction (already built, and already emits `race_id` + `calling_id` per the migration above). **⛨ saga:** `NewGame.construct` takes `creation` as a plain `Dictionary` — keep it that way. The creation *scene* produces that dict but must not become the only thing that can (a saga synthesizes it and skips the UI). *§2: state · depends on the creation model (M0) + Theme · goal: build a character.*
 - ○ **Title → creation → shell flow (M4-c)** — wire the title screen's *new game* path into character creation and on into the M3 shell, without hardcoding a `new game → creation → world` linear flow (the saga's fourth entry path, §M3, must still be addable later). *§2: n/a (flow) · depends on M4-b + the Title screen (M3) · goal: a playable start-to-shell loop.*