Planner uses generic acceptance criteria; derive them from the issue body

[Svaag]

planner_node (src/hyrule_engineering_loop/nodes.py:336-339) hardcodes a generic 3-item acceptance list for every task spec:

1. implemented within allowed paths
2. selected gates pass
3. no secret material

So the loop's formal definition-of-done (used by role judgment + grading) ignores the issue's own acceptance criteria. (#9 fixed the related problem of the implementer not seeing the body at all; this is the remaining half.)

Ask

When the issue body contains an acceptance section (e.g. ## Acceptance / ## Acceptance criteria with bullet/numbered items), parse those into acceptance_criteria so role judgments grade against the real spec; fall back to the generic template when absent. Keep it deterministic (no LLM dependency in the planner) and robust to varied markdown.

Acceptance

• A task spec built from an issue with an explicit acceptance section carries those items as acceptance_criteria.
• Issues without one keep the current generic template.
• ruff / mypy --strict / pytest / evals stay green.