fix(sessions): crystallize summary omits approved GOAL proposals

[kurosawareiji7007-hub]

What happened

sessions._approved_artifact_ids_for_session only includes CLAIM/PAGE/ENTITY/RELATION when building the crystallize summary page. After first-class goals (#427), an approved GOAL filed in the session never appears under "Crystallized artifacts".

Expected

Approved goals in the session are listed like other create-kind artifacts. DELETE stays excluded.

Repro

sess = session_start(store, agent="a", task="t")
pr = propose_goal(store, title="ship", proposed_by="a", session_id=sess.id)
goal = approve(store, pr.id, approved_by="h")
session_end(store, sess.id)
page = get_page(crystallize(store, sess.id, approver="h")["summary_page_id"])
# goal.id missing from page.body today