docs(aggregation): drop section-banner headings from docstrings (#1126)

Two method docstrings opened with Markdown-style section banners
(# Overview and # The message bindings) that render as headings
inside Google-style docstrings and are inconsistent with every
other method in the file.

Drop the banner lines; the prose beneath stands alone unchanged.
Docs-only change; just check passes.

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

Author: tcoratger

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

@@ -60,8 +60,6 @@ def aggregate(
         """
         Fold fresh signatures and child proofs into one single-message proof.
 
-        # Overview
-
         Two kinds of contribution merge into one proof.
 
         - A fresh signer contributes a single raw signature.
@@ -312,8 +310,6 @@ def verify(
         """
         Verify this multi-message proof against its per-component bindings.
 
-        # The message bindings
-
         Each component is checked against one message and slot supplied by the caller.
         Without that binding the proof would accept attacker-chosen data.
         That data could resolve to the same keys.