feat(realism): LLM enrichment for user-class file bodies

Stage 6 of the realism migration. User-class file bodies (note,
todo, draft, script) optionally get LLM-authored content; system
classes (cron / daemon logs, /tmp caches) stay template-only because
formulaic *is* the right look for them.

New surface:

- realism.llm.circuit.LLMCircuitBreaker — process-local sliding-window
  breaker. 3 consecutive failures trip open; 60s cooldown to half-open;
  half-open success closes, failure re-opens. Protects the orchestrator
  tick from sustained Ollama wedges (per-call timeout already covers
  one-shot hangs).
- realism.prompts._style — em-dash suppression lifted from the
  email prompt. Persona.uses_llms_heavily opts out per the
  feedback_em_dash_llm_tell.md memory. Includes strip_em_dashes
  belt-and-braces sub for output that slipped past the prompt rule.
- realism.prompts.filebody — class-conditioned prompts (note / todo
  / draft / script) with persona context, language pinning, output
  shape rule.
- realism.bodies.make_body_with_llm — async wrapper around make_body
  that calls the LLM when one is provided AND the breaker allows.
  Falls back to template on timeout / error / empty / system-class.

Wiring:

- scheduler.pick_file accepts optional llm + llm_breaker + llm_timeout.
  When the planner picks a create action and the content_class is a
  user-class, the body_hint is replaced with the LLM-authored body
  (or falls back to the deterministic body_hint).
- orchestrator.worker constructs get_llm() at startup gated by
  DECNET_REALISM_LLM env var (any non-empty value enables; empty /
  "off" / "none" / "0" disables). Passes llm + breaker through every
  tick.
- decnet orchestrate gains --llm/--no-llm flag overriding the env var.

decnet/realism/prompts/_style.py

@@ -0,0 +1,39 @@
+"""Shared stylometric guards for LLM-bound prompts.
+
+Lifted from the original ``orchestrator.emailgen.prompt`` em-dash
+block so file-class prompts (note / todo / draft / script bodies)
+pick up the same suppression.  Per the
+``feedback_em_dash_llm_tell.md`` memory: em-dashes (—) are a strong
+LLM-authorship tell, suppress by default; allow only for personas
+explicitly opted in via ``EmailPersona.uses_llms_heavily``.
+"""
+from __future__ import annotations
+
+from decnet.realism.personas import EmailPersona
+
+
+_SUPPRESS_RULE = (
+    "Do NOT use em-dashes (—). Use commas, periods, or "
+    "parentheses instead. Em-dashes are a tell."
+)
+_ALLOW_RULE = (
+    "Em-dashes are fine — this persona uses them naturally. "
+    "Write in your usual style."
+)
+
+
+def em_dash_rule(persona: EmailPersona) -> str:
+    """Return the em-dash instruction line for *persona*'s prompt."""
+    if persona.uses_llms_heavily:
+        return _ALLOW_RULE
+    return _SUPPRESS_RULE
+
+
+def strip_em_dashes(text: str, persona: EmailPersona) -> str:
+    """Belt-and-braces: even with the prompt rule, small models leak
+    em-dashes occasionally.  Substitute with comma+space so the
+    output reads naturally; opt-in personas pass through unchanged.
+    """
+    if persona.uses_llms_heavily:
+        return text
+    return text.replace("—", ", ").replace("–", ", ")

decnet/realism/prompts/filebody.py

@@ -0,0 +1,91 @@
+"""Class-conditioned prompt builder for user-class file bodies.
+
+Stage 6 of the realism migration.  Only user-classes (``note``,
+``todo``, ``draft``, ``script``) get LLM enrichment — system-class
+content (cron logs, daemon logs, /tmp caches) is *supposed* to look
+formulaic, and an LLM-authored cron log is more suspicious than a
+templated one.
+
+The prompt asks for *short* output (LLM-authored ten-page essays in
+``~/notes.txt`` are an instant tell) and pins the exit shape so the
+worker doesn't need to scrape boilerplate.  Em-dash suppression
+flows through :mod:`decnet.realism.prompts._style`.
+"""
+from __future__ import annotations
+
+from decnet.realism.personas import EmailPersona
+from decnet.realism.prompts._style import em_dash_rule
+from decnet.realism.taxonomy import ContentClass
+
+
+_LANGUAGE_NAMES = {
+    "en": "English", "es": "Spanish", "pt": "Portuguese",
+    "fr": "French", "de": "German", "it": "Italian",
+    "nl": "Dutch", "ja": "Japanese", "zh": "Chinese",
+}
+
+
+def _lang_label(code: str) -> str:
+    return _LANGUAGE_NAMES.get((code or "en").lower(), code or "English")
+
+
+_CLASS_GUIDANCE: dict[ContentClass, str] = {
+    ContentClass.NOTE: (
+        "A personal note file the persona keeps on their dev box.  "
+        "2–6 short lines.  Mix of TODOs, half-formed thoughts, "
+        "shorthand reminders.  NOT a polished document.  No headers "
+        "or markdown sections."
+    ),
+    ContentClass.TODO: (
+        "A markdown TODO list the persona keeps on their dev box.  "
+        "3–8 items in `- [ ] item` / `- [x] item` form.  Some checked, "
+        "some not.  Items are short, work-flavoured, lowercase, no "
+        "prose paragraphs.  No headers.  No introductory sentence."
+    ),
+    ContentClass.DRAFT: (
+        "A short draft email or memo the persona is working on.  "
+        "2–4 short paragraphs, conversational tone.  No subject line, "
+        "no headers — this is the body in a notes file, not a sent "
+        "email.  Sign off the way the persona would in their voice."
+    ),
+    ContentClass.SCRIPT: (
+        "A short utility script the persona wrote.  Pick a plausible "
+        "interpreter (bash or python3) and start with the matching "
+        "shebang.  10–25 lines.  Real-feeling intent (a backup, a "
+        "log rotation, a cleanup).  Inline comments allowed but sparse."
+    ),
+}
+
+
+def build(
+    content_class: ContentClass,
+    persona: EmailPersona,
+) -> str:
+    """Return a prompt for one body of *content_class* by *persona*.
+
+    Output the LLM is expected to produce: *just the file body*, no
+    commentary, no markdown fences.  Caller substitutes em-dashes
+    server-side via :func:`decnet.realism.prompts._style.strip_em_dashes`
+    as a belt-and-braces guard.
+    """
+    guidance = _CLASS_GUIDANCE.get(content_class)
+    if guidance is None:
+        raise KeyError(
+            f"no filebody prompt registered for content_class={content_class!r}"
+        )
+    language = _lang_label(persona.language or "en")
+    return (
+        f"You are writing one short file the persona below would "
+        f"plausibly keep on their dev box.\n\n"
+        f"Persona:\n"
+        f"- Name: {persona.name}\n"
+        f"- Role: {persona.role}\n"
+        f"- Tone: {persona.tone_custom if persona.tone == 'custom' and persona.tone_custom else persona.tone}\n\n"
+        f"File class: {content_class.value}\n"
+        f"Guidance: {guidance}\n\n"
+        f"Hard rules:\n"
+        f"1. Write the file body in {language}. Do not translate or code-switch.\n"
+        f"2. {em_dash_rule(persona)}\n"
+        f"3. Output ONLY the file body. No commentary, no markdown "
+        f"   fences, no preamble like 'Here is the file:'.\n"
+    ).strip()