fix(creation-model): migrate stray class_id/allowed_classes copies

The canon-log schema and NewGame code already migrated to race_id/
calling_id + allowed_callings, but two copies of the roster outside
that schema were missed, and no parity test guards them:

- docs/canon-log.md (the cross-boundary contract doc) still documented
  the OLD player shape and allowed_classes. Anyone building a player
  block from the doc would get a 422.
- .claude/skills/world-building's schema reference still emitted
  allowed_classes with two dead calling ids (assassin, priest). Author
  a new origin with that skill and it fails origin.schema.json
  (additionalProperties: false, allowed_callings required) AND, if that
  ever loosened, silently allows zero callings at runtime.

Also:
- add schema tests rejecting a dead class_id field and an unknown
  calling_id (priest)
- guard NewGame._validate's container types (spend/skills) so a
  malformed JSON round-trip (null spend, string skills) produces a
  front-loaded error list instead of a GDScript runtime crash
- extend the no-mechanics-in-content test to db.races, not just
  db.callings
- rewrite the roadmap's M4 bullet: the two contract migrations landed;
  only the creation screen and title->creation->shell flow remain

client: 250/250. api: 74 passed, 2 skipped. content_build --check: clean.

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

docs/canon-log.md

@@ -27,7 +27,7 @@ Full field rules live in `canon-log.schema.json`. Summary:
 ```json
 {
   "schema_version": 1,
-  "player":   { "name": "…", "class_id": "sellsword|assassin|priest", "luck_descriptor": "…" },
+  "player":   { "name": "…", "race_id": "human|elf|dwarf|beastfolk", "calling_id": "sellsword|reaver|cutpurse|trapper|hedge_mage|bonesetter|bloodsworn", "luck_descriptor": "…" },
   "location": { "id": "…", "name": "…" },
   "party":    [ { "id": "…", "name": "…", "disposition": -100..100 } ],
   "recent_events":     ["… (≤5, rolling)"],
@@ -39,9 +39,13 @@ Full field rules live in `canon-log.schema.json`. Summary:
 
 **The §7 boundary (enforced structurally).** The schema sets
 `additionalProperties: false` on the root and on `player`, and `player` admits
-only `name`, `class_id`, `luck_descriptor`. **Numeric Luck, stats, HP/MP, and
-inventory cannot be represented in the canon log** — the AI never sees a number
-it could use to calculate Luck. Only `luck_descriptor` (e.g. "Fortune spits on
+only `name`, `race_id`, `calling_id`, `luck_descriptor`. `race_id` and
+`calling_id` are there so the Narrator and NPCs can *describe* the player (a
+"beastfolk cutpurse" reads different scene text than a "dwarf bonesetter") —
+they are identity for prose, not mechanics. **Numeric Luck, stats, HP/MP, and
+inventory cannot be represented in the canon log** — the mechanical sheet stays
+in `GameState` and never reaches the log, and the AI never sees a number it
+could use to calculate Luck. Only `luck_descriptor` (e.g. "Fortune spits on
 you") crosses the boundary.
 
 All string ids match `^[a-z0-9_]+$`.
@@ -59,7 +63,7 @@ Full rules in `origin.schema.json`. An origin seeds the initial log:
   "disposition_overrides": { "<npc_id>": -100..100 },
   "inventory_grants": [ { "item_id": "…", "qty": 1.. } ],
   "start_quest_id": "…|null",
-  "build_constraints": { "allowed_classes": ["sellsword",…], "luck_modifier": 0 }
+  "build_constraints": { "allowed_callings": ["sellsword",…], "luck_modifier": 0 }
 }
 ```