feat(dsh-plugin-browserskill): add the web client half with a browser_screenshot toolview

Make the package dual-face: a dsh.client declaration (platform 'web')
plus an exports["./client"] bundle built in dsh's closure-factory shape
(window.__ModuleLoader__.load handoff, platform modules external,
everything else inlined, CSS Modules via lightningcss).

The client registers a keyed 'tool.call.toolview' view for
browser_screenshot that keeps the terminal block (command + output) and,
when the settled result carries an image block, resolves the durable
attachment through the client session's authorized readAttachment RPC
and renders it with the shared MessageImage thumbnail/lightbox atoms.
Path-only results render unchanged; every other browser_* tool keeps
the stock terminal card.

Tests: view-model derivation (running/ok/error, image vs path-only),
component rendering through @testing-library/react + happy-dom, and the
registration key. biome.json now excludes the package's lib/ build
output (same treatment as dist/).

biome.json

@@ -39,6 +39,7 @@
       "**",
       "!**/node_modules/**",
       "!**/dist/**",
+      "!packages/dsh-plugin-browserskill/lib/**",
       "!**/target/**",
       "!**/.wxt/**",
       "!**/.output/**",