fix(teacher): import _TEACHER_SYSTEM_PROMPT from its current module

[DocFurious]

Fixes #4962.

Problem

src/teacher_escalation.py:236 imports _TEACHER_SYSTEM_PROMPT from
src.ai_interaction, where it is no longer defined. The symbol now lives in
src/agent_tools/model_interaction_tools.py.

Result: every teacher escalation raises ImportError before the teacher is
ever called. Because maybe_escalate() is fire-and-forget, the feature fails
silently — no skill is distilled and the user sees nothing but a log warning.

Reproduced on main @ cf4e240 and dev @ d8a2059 (both 2026-07-23).

Fix

Point the import at the module that actually defines the constant:

from src.ai_interaction import _resolve_model
from src.agent_tools.model_interaction_tools import _TEACHER_SYSTEM_PROMPT

Notes

This is the same change as #4962 / PR #4967. That PR appears to have been
lost rather than reverted — the fix is absent from both branches.

Verification

With the fix applied, _call_teacher() completes against a configured
teacher endpoint and returns a valid skill payload (name, description,
when_to_use, procedure steps) that passes evaluate_turn_regex.

[github-actions]

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