docs(spec): fix duplicated phrasing and filler in lstar docs (leanEthereum#880)

Pure documentation cleanup, no behavior change:

- Remove the doubled "single-message single-message" / "single-message
  aggregate single-message aggregated" phrasing (a bad find/replace) in
  the aggregate-proof verify docstring and the fork-choice comment.
- Drop the "Represents a ..." filler from the Slot, ValidatorIndex,
  Validator, and Checkpoint summaries; docstring summaries are noun
  phrases, not "Represents ..." sentences.
- Remove the banned backticks around "delta" in the justifiability
  docstring.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tcoratger

src/lean_spec/spec/forks/lstar/containers/aggregation.py

@@ -132,7 +132,7 @@ def verify(
         slot: Slot,
     ) -> None:
         """
-        Verify this single-message single-message aggregate proof against a public_key set.
+        Verify this single-message aggregate proof against a set of public keys.
 
         Args:
             public_keys: PublicKeys for the validators named by participants.

src/lean_spec/spec/forks/lstar/containers/checkpoint.py

@@ -11,7 +11,7 @@
 
 class Checkpoint(Container):
     """
-    Represents a checkpoint in the chain's history.
+    A checkpoint in the chain's history.
 
     A checkpoint marks a specific moment in the chain.
 

src/lean_spec/spec/forks/lstar/containers/identifiers.py

@@ -10,7 +10,7 @@ class SubnetId(Uint64):
 
 
 class ValidatorIndex(Uint64):
-    """Represents a validator's unique index as a 64-bit unsigned integer."""
+    """A validator's index in the registry, as a 64-bit unsigned integer."""
 
     @classmethod
     def proposer_for_slot(cls, slot: Slot, num_validators: Uint64) -> "ValidatorIndex":

src/lean_spec/spec/forks/lstar/containers/validator.py

@@ -6,7 +6,7 @@
 
 
 class Validator(Container):
-    """Represents a validator's static metadata and operational interface."""
+    """A validator's static metadata and operational interface."""
 
     attestation_public_key: Bytes52
     """XMSS public key for signing attestations."""

src/lean_spec/spec/forks/lstar/fork_choice.py

@@ -394,7 +394,7 @@ def on_gossip_aggregated_attestation(
             for validator_index in validator_indices
         ]
 
-        # Verify the single-message aggregate single-message aggregated proof.
+        # Verify the single-message aggregate proof.
         try:
             aggregated_proof.verify(
                 public_keys=public_keys,

src/lean_spec/spec/forks/lstar/slot.py

@@ -16,7 +16,7 @@
 
 
 class Slot(Uint64):
-    """Represents a slot number as a 64-bit unsigned integer."""
+    """A slot number, as a 64-bit unsigned integer."""
 
     def justified_index_after(self, finalized_slot: "Slot") -> int | None:
         """
@@ -36,7 +36,7 @@ def is_justifiable_after(self, finalized_slot: "Slot") -> bool:
         Checks if this slot is a valid candidate for justification after a given finalized slot.
 
         According to the 3SF-mini specification, a slot is justifiable if its
-        distance (`delta`) from the last finalized slot is:
+        distance (delta) from the last finalized slot is:
           1. Less than or equal to 5.
           2. A perfect square (e.g., 9, 16, 25...).
           3. A pronic number (of the form x^2 + x, e.g., 6, 12, 20...).