Build a decision-sufficient ObservationView from the raw snapshot and
render it as a deterministic line-based prompt string. The raw to_dict()
is ~64 KB (~16k tokens) for a 7-combatant encounter; the compact view
renders at ~15.7 KB (~3.9k tokens, 24% of raw), under the 4k-token
ceiling of the phase-2 architecture doc.
Compaction: sparse terrain/elevation/threatened grids, per-combatant
key selection (occupied_cells, abilities, skills, initiative_mod/total,
temp_hp_rounds_left, features, carried_items, weapon_damage, aware,
alignment, armor_spell_failure, arcane_caster, run_rounds dropped),
attacks compacted to formula+type damage strings, spells to 7
decision-relevant fields, pair target_index replaced by the stable
combatant id, condition_definitions dropped. Attacks and spells render
as positional tuples declared by attack_fields/spell_fields legend
lines, with '-' for missing values.
Tests pin the size bounds (compact < 0.25 x raw and < 16000 bytes), the
sparse-grid contract, the dropped-key contract and the deterministic
id/render contract on a caster-heavy 3v4 representative battle.
