feat(cli+mcp): vertical extractor support (28 extractors discoverable + callable)

Wires the vertical extractor catalog into both the CLI and the MCP
server so users don't have to hit the HTTP API to invoke them. Same
semantics as `/v1/scrape/{vertical}` + `/v1/extractors`.

CLI (webclaw-cli):
- New subcommand `webclaw extractors` lists all 28 extractors with
  name, label, and sample URL. `--json` flag emits the full catalog
  as machine-readable JSON.
- New subcommand `webclaw vertical <name> <url>` runs a specific
  extractor and prints typed JSON. Pretty-printed by default; `--raw`
  for single-line. Exits 1 with a clear "URL does not match" error
  on mismatch.
- FetchClient built with Firefox profile + cloud fallback attached
  when WEBCLAW_API_KEY is set, so antibot-gated verticals escalate.

MCP (webclaw-mcp):
- New tool `list_extractors` (no args) returns the catalog as
  pretty-printed JSON for in-session discovery.
- New tool `vertical_scrape` takes `{name, url}` and returns typed
  JSON. Reuses the long-lived self.fetch_client.
- Tool count goes from 10 to 12. Server-info instruction string
  updated accordingly.

Tests: 215 passing, clippy clean. Manual surface-tested end-to-end:
CLI prints real Reddit/github/pypi data; MCP JSON-RPC session returns
28-entry catalog + typed responses for pypi/requests + rust-lang/rust
in 200-400ms.

Version bumped to 0.5.2 (minor for API additions, backwards compatible).

CHANGELOG.md

@@ -3,6 +3,20 @@
 All notable changes to webclaw are documented here.
 Format follows [Keep a Changelog](https://keepachangelog.com/).
 
+## [0.5.2] — 2026-04-22
+
+### Added
+- **`webclaw vertical <name> <url>` subcommand on the CLI.** Runs a specific vertical extractor and prints typed JSON (pretty-printed by default, `--raw` for single-line). Example: `webclaw vertical reddit https://www.reddit.com/r/rust/comments/abc/` returns `{post: {title, author, points, ...}, comments: [...]}`. URL-mismatch errors surface cleanly as `"URL '...' does not match the '...' extractor"` on stderr with exit code 1.
+
+- **`webclaw extractors` subcommand on the CLI.** Lists all 28 vertical extractors with name, label, and one URL pattern sample. `--json` emits the full catalog as JSON (same shape as `GET /v1/extractors`) for tooling. Covers discovery for users who don't know which vertical to pick.
+
+- **`vertical_scrape` and `list_extractors` tools on `webclaw-mcp`.** Claude Desktop / Claude Code users can now call any of the 28 extractors by name from an MCP session. Tool count goes from 10 to 12. `list_extractors` takes no args and returns the full catalog; `vertical_scrape` takes `{name, url}` and returns the typed JSON payload. Antibot-gated verticals still auto-escalate to the webclaw cloud API when `WEBCLAW_API_KEY` is set.
+
+### Changed
+- Server-info instruction string in `webclaw-mcp` now lists all 12 tools (previously hard-coded 10). Also `webclaw --help` on the CLI now shows the three subcommands: `bench`, `extractors`, `vertical`.
+
+---
+
 ## [0.5.1] — 2026-04-22
 
 ### Added