docs: update context-discipline for EGG_REAL_BACKEND_WINDOW injection [doc-updater] - #3348

No agent-mode design concerns. This is a documentation-only change updating the EGG_REAL_BACKEND_WINDOW env-var description to reflect always-injected behaviour at event spawn time (#3316); it touches no prompt construction, pre-fetching, output-format, post-processing, or model-identifier surfaces.

— Authored by egg

Approve. Doc-only change; every factual claim verified against the code at HEAD.

I treated this as an accuracy review (the diff makes specific claims about runtime behaviour) and traced each one to source:

• "the orchestrator always computes real_backend_window(model) and exports the integer here via _ExecutorEventSpawner.spawn_event (#3316)" — confirmed. _ExecutorEventSpawner.spawn_event (orchestrator/concurrent_executor.py:166, class at :142) sets env["EGG_REAL_BACKEND_WINDOW"] = str(real_window) at :195, unconditionally — not gated behind a discipline/measurement flag — so "always injected" is accurate. The value comes from _build_event_spawn_params:659 (real_window = real_backend_window(decision.claude_code_alias)), and real_backend_window(model) exists at orchestrator/agent_model_resolution.py:468. The method/class name in the doc matches exactly.
• "the measurement's orchestrator-import fallback is inert on the production event-pump path" — confirmed. _resolve_real_window (shared/egg_agent/measurement.py:208) reads $EGG_REAL_BACKEND_WINDOW first (:229); the from orchestrator.agent_model_resolution import real_backend_window fallback at :240 always raises in-pod (orchestrator off PYTHONPATH).
• "In dev/CI … the measurement also imports the helper directly" — confirmed (:239-247).
• "Both window-relative metrics degrade to None on pre-#3316 pods where the export is absent" — confirmed: with no override and no importable orchestrator, resolution returns None.
• Parallel phrasing with EGG_RESEED_THRESHOLD — the rewritten row and the new "Setting the flags in production" sentence are consistent with the existing EGG_RESEED_THRESHOLD row (:234) and the #3284 paragraph.
• Issue reference — #3316 exists, is CLOSED, and its title ("Inject EGG_REAL_BACKEND_WINDOW into agent event pods") matches the doc's description of its effect.

No inaccuracies, no stale/contradicting references elsewhere in the docs (checked docs/ for EGG_REAL_BACKEND_WINDOW / real_backend_window). The doc now correctly reflects post-#3316 behaviour. No blocking or non-blocking issues.

— Authored by egg