refactor(contract)!: class_id -> calling_id, and the log gains race_id

class_id is the rulebook's word; the world has callings — that was the whole §17
reconcile. The contract the Narrator reads should say what the world says. There
are no saves (M9) and no deployed clients, so this is as cheap as it will ever be
and strictly more expensive every milestone after.

race_id reaches the log because the AI must be able to describe the player:
api/app/prompts.py rendered 'a sellsword' and now renders 'a beastfolk cutpurse'.
It humanizes the id (the model must never read 'hedge_mage') and picks the right
article ('an elf', not 'a elf').

LogPlayer's hardcoded CLASSES const is deleted — the roster is Callings.IDS. A
parity test reads the JSON Schema from the client and asserts its enum equals the
code, so the two sides of the HTTP boundary cannot drift.

The deserter allowed three callings that no longer exist. He now allows all seven;
a thematic gate is a content decision for the Greywater authoring.

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

api/app/prompts.py

@@ -12,6 +12,23 @@ from pathlib import Path
 _PROMPT_DIR = Path(__file__).resolve().parent.parent / "prompts"
 
 
+def _humanize(id_: str) -> str:
+    """Ids are snake_case; the model should read prose. hedge_mage -> hedge-mage."""
+    return id_.replace("_", "-")
+
+
+def _article(word: str) -> str:
+    return "an" if word[:1].lower() in "aeiou" else "a"
+
+
+def _describe_player(player: dict) -> str:
+    """'Aldric, a beastfolk cutpurse' — what the AI narrates the player as."""
+    race = _humanize(player.get("race_id", ""))
+    calling = _humanize(player.get("calling_id", ""))
+    name = player.get("name", "")
+    return f"{name}, {_article(race)} {race} {calling}".strip()
+
+
 @lru_cache(maxsize=None)
 def system_prompt(role: str) -> str:
     text = (_PROMPT_DIR / f"{role}.md").read_text(encoding="utf-8")
@@ -50,7 +67,7 @@ def render_digest(canon_log: dict) -> str:
     descriptor = player.get("luck_descriptor")
     if descriptor:
         lines.append(f"Fortune: {descriptor}")
-    lines.append(f"Player: {player.get('name', '')}, a {player.get('class_id', '')}")
+    lines.append(f"Player: {_describe_player(player)}")
 
     lines.append("")
     lines.append("Describe the scene as it is now.")
@@ -104,7 +121,7 @@ def render_npc_digest(
             lines.append(f"Active quest: {quest.get('name', '')} — {quest.get('objective', '')}")
 
     player = canon_log.get("player", {})
-    lines.append(f"The player is {player.get('name', '')}, a {player.get('class_id', '')}.")
+    lines.append(f"The player is {_describe_player(player)}.")
 
     lines.append("")
     lines.append(f'The player says to you: "{utterance}"')