style: apply ruff format to client.py, execution.py, server.py

Add required 2 blank lines between top-level function/class definitions.
Fixes CI `ruff format --check` failure.

Author: nficano

src/arcp/_client/client.py

@@ -38,16 +38,19 @@
 
 _LOG = get_logger("arcp.client")
 
+
 def _now_iso() -> str:
     return datetime.now(UTC).isoformat().replace("+00:00", "Z")
 
+
 @dataclass(frozen=True)
 class AutoAckOptions:
     """Coalesce acks: send `session.ack` every `every_n` events, or every `interval_sec`."""
 
     every_n: int = 100
     interval_sec: float = 1.0
 
+
 class ARCPClient:
     """ARCP client: open/resume a session, submit jobs, observe events."""
 
@@ -276,4 +279,5 @@ async def close(self, *, reason: str = "client.close") -> None:
     async def aclose(self) -> None:
         await self.close()
 
+
 __all__ = ("ARCPClient", "AutoAckOptions")

src/arcp/_messages/execution.py

@@ -29,6 +29,7 @@
 _AGENT_NAME_RE = re.compile(r"^[a-zA-Z][a-zA-Z0-9._-]*$")
 _AGENT_VERSION_RE = re.compile(r"^[a-zA-Z0-9][a-zA-Z0-9._-]*$")
 
+
 def parse_agent_ref(ref: str) -> tuple[str, str | None]:
     """Parse `name` or `name@version`; raise `ValueError` on malformed input."""
     if "@" in ref:
@@ -40,12 +41,15 @@ def parse_agent_ref(ref: str) -> tuple[str, str | None]:
         raise ValueError(f"invalid agent name: {ref!r}")
     return ref, None
 
+
 def format_agent_ref(name: str, version: str | None) -> str:
     """Inverse of `parse_agent_ref`."""
     return f"{name}@{version}" if version else name
 
+
 _BUDGET_AMOUNT_RE = re.compile(r"^([A-Za-z][A-Za-z0-9]{0,9}):([0-9]+(?:\.[0-9]+)?)$")
 
+
 def parse_budget_amount(amount: str) -> tuple[str, Decimal]:
     """Parse `currency:decimal`; raise `ValueError` on malformed input."""
     m = _BUDGET_AMOUNT_RE.match(amount)
@@ -60,12 +64,15 @@ def parse_budget_amount(amount: str) -> tuple[str, Decimal]:
         raise ValueError("budget amount must be non-negative")
     return currency, value
 
+
 def format_budget_amount(currency: str, value: Decimal) -> str:
     return f"{currency}:{value}"
 
+
 Lease = dict[str, list[str]]
 """A lease maps capability namespace to a list of glob patterns."""
 
+
 def _ensure_utc_iso8601(value: str) -> datetime:
     """Parse a strict UTC ISO 8601 timestamp (`Z` or `+00:00` only)."""
     if not isinstance(value, str):
@@ -79,6 +86,7 @@ def _ensure_utc_iso8601(value: str) -> datetime:
         raise ValueError(f"expires_at must be UTC: {value!r}")
     return dt
 
+
 class LeaseConstraints(BaseModel):
     """Optional lease constraints (v1.1 §9.5)."""
 
@@ -93,6 +101,7 @@ def _check_expires_at(cls, v: str | None) -> str | None:
         _ensure_utc_iso8601(v)
         return v
 
+
 class JobSubmitPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     agent: str
@@ -110,6 +119,7 @@ def _check_agent(cls, v: str) -> str:
         parse_agent_ref(v)
         return v
 
+
 class CredentialConstraintsPayload(BaseModel):
     model_config = ConfigDict(extra="allow", populate_by_name=True)
     cost_budget: tuple[str, ...] = Field(default=(), alias="cost.budget")
@@ -140,11 +150,13 @@ class JobAcceptedPayload(BaseModel):
     trace_id: str | None = None
     credentials: tuple[CredentialPayload, ...] | None = None
 
+
 class JobCancelPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     reason: str
     code: str | None = None
 
+
 class JobEventPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     kind: str
@@ -158,6 +170,7 @@ def _check_kind(cls, v: str) -> str:
             return v
         raise ValueError(f"unknown event kind: {v!r}")
 
+
 class JobResultPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     final_status: Literal["success", "cancelled", "timed_out"]
@@ -167,6 +180,7 @@ class JobResultPayload(BaseModel):
     summary: str | None = None
     completed_at: str
 
+
 class JobErrorPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     final_status: Literal["error"] = "error"
@@ -176,12 +190,14 @@ class JobErrorPayload(BaseModel):
     completed_at: str
     details: dict[str, Any] | None = None
 
+
 class JobSubscribePayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     job_id: str
     history: bool = False
     from_event_seq: int | None = Field(default=None, ge=0)
 
+
 class JobSubscribedPayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     request_id: str
@@ -194,10 +210,12 @@ class JobSubscribedPayload(BaseModel):
     subscribed_from: int = 0
     replayed: int = 0
 
+
 class JobUnsubscribePayload(BaseModel):
     model_config = ConfigDict(extra="allow")
     job_id: str
 
+
 __all__ = (
     "EVENT_KINDS",
     "ArtifactRefBody",

src/arcp/_runtime/server.py

@@ -42,11 +42,14 @@
 
 _LOG = get_logger("arcp.runtime.server")
 
+
 def _now_iso() -> str:
     return datetime.now(UTC).isoformat().replace("+00:00", "Z")
 
+
 JobAuthorizationPolicy = Callable[["AuthorizationContext"], bool]
 
+
 @dataclass(frozen=True)
 class AuthorizationContext:
     """Inputs to the per-job authorization policy used by `list_jobs` and `subscribe`."""
@@ -55,17 +58,20 @@ class AuthorizationContext:
     job: Job
     operation: str  # "list" | "subscribe" | "cancel"
 
+
 def _default_authz_policy(ctx: AuthorizationContext) -> bool:
     """Same-principal default: requester must own the job (§14)."""
     return ctx.job.submitter_principal == ctx.requester_principal
 
+
 @dataclass
 class _AgentRegistration:
     name: str
     versions: dict[str, Agent] = field(default_factory=dict)
     default_version: str | None = None
     bare: Agent | None = None  # registered without a version
 
+
 class ARCPRuntime:
     """Server-side runtime: register agents, accept transports, dispatch envelopes."""
 
@@ -220,6 +226,7 @@ async def close(self) -> None:
                 await task
         await self.event_log.close()
 
+
 from . import _handlers  # noqa: E402
 
 _DISPATCH_TABLE: dict[