feat(rules): add the surprise round

SRD Surprise: when some but not all combatants are aware of their
opponents, a surprise round precedes round 1. Aware combatants take a
single standard OR move action plus free actions (swift and full-round
are dropped, full_attack collapses to one standard attack, withdraw
survives as the Restricted Withdraw standard); unaware combatants skip
their turn. New Combatant.aware flag (default true, parsed at the JSON
boundary) keeps every existing encounter bit-identical, exposed in the
observation snapshot. Unaware combatants are not flagged flat-footed
(documented simplification).

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/pf1e_simulator/loaders/combatant.py

@@ -208,6 +208,8 @@ def load_combatant(path: Path) -> Combatant:
 
     ``features`` in the JSON are a list of feat name strings resolved via
     ``_resolve_feat``.  ``spells`` are passed through as-is (list of strings).
+    The ``aware`` flag (SRD "Surprise") is a plain boolean of the
+    ``Combatant`` schema (default ``true``), so it parses directly here.
     """
     try:
         raw = path.read_text(encoding="utf-8")