feat: CLI --research flag + MCP cloud fallback + structured research output

- --research "query": deep research via cloud API, saves JSON file with
  report + sources + findings, prints report to stdout
- --deep: longer, more thorough research mode
- MCP extract/summarize: cloud fallback when no local LLM available
- MCP research: returns structured JSON instead of raw text
- Bump to v0.3.7

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -3055,7 +3055,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-cli"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "clap",
  "dotenvy",
@@ -3075,7 +3075,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-core"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "ego-tree",
  "once_cell",
@@ -3093,7 +3093,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-fetch"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "bytes",
  "calamine",
@@ -3115,7 +3115,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-llm"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "async-trait",
  "reqwest",
@@ -3128,7 +3128,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-mcp"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "dotenvy",
  "reqwest",
@@ -3148,7 +3148,7 @@ dependencies = [
 
 [[package]]
 name = "webclaw-pdf"
-version = "0.3.6"
+version = "0.3.7"
 dependencies = [
  "pdf-extract",
  "thiserror",