docs: drop redundant body H1s that duplicated frontmatter title

- concepts/streaming.md: remove '# Streaming + chunking'.
- reference/session-management-compaction.md: remove Title Case H1
  '# Session Management & Compaction (Deep Dive)'.
- plugins/voice-call.md: remove '# Voice Call (plugin)'.

CLI pages keep their command-formatted body H1s since that is the repo
convention and the formatting is not expressible in frontmatter.

docs/concepts/streaming.md

@@ -7,8 +7,6 @@ read_when:
 title: "Streaming and chunking"
 ---
 
-# Streaming + chunking
-
 OpenClaw has two separate streaming layers:
 
 - **Block streaming (channels):** emit completed **blocks** as the assistant writes. These are normal channel messages (not token deltas).

docs/plugins/voice-call.md

@@ -6,8 +6,6 @@ read_when:
 title: "Voice call plugin"
 ---
 
-# Voice Call (plugin)
-
 Voice calls for OpenClaw via a plugin. Supports outbound notifications and
 multi-turn conversations with inbound policies.
 

docs/reference/session-management-compaction.md

@@ -7,9 +7,7 @@ read_when:
 title: "Session management deep dive"
 ---
 
-# Session Management & Compaction (Deep Dive)
-
-This document explains how OpenClaw manages sessions end-to-end:
+This page explains how OpenClaw manages sessions end-to-end:
 
 - **Session routing** (how inbound messages map to a `sessionKey`)
 - **Session store** (`sessions.json`) and what it tracks