fix: drop tool-web subpath exports, align with tool-bash single-entry shape

The web tool package exposed ./search and ./fetch as standalone subpath
plugins, but nothing consumed them, the RFC never called for them, and the
sibling dsh-tool-bash (also a multi-tool consumer) ships a single entry and
selects tools via config. The extra entries also tripped the workspace
constraints gate, whose expected `files` list covers single-entry and bin
packages but not a non-bin multi-entry one.

Collapse to a single `.` entry: drop the ./search|./fetch exports and their
lib/*.js from package.json files, delete the per-package tsdown override (the
root config's lib/types/index.js entry now suffices), and remove the
plugin-shaped name/inject exports from search.ts/fetch.ts (renaming each
apply to its applyWeb{Search,Fetch}Tool helper, still composed by the root
plugin and re-exported from the index). Selective enablement stays via the
existing { search?, fetch? } config. Docs updated to match.

packages/web/tool-web/src/index.ts

@@ -1,8 +1,7 @@
 /**
  * The model-facing web tool suite (`web_search`, `web_fetch`) over the `ctx.web`
  * seam. This root plugin registers the tools the product has ENABLED, composing
- * the per-tool registration helpers; each tool is also exposed as a subpath
- * plugin (`@deepseek-ai/dsh-tool-web/search`, `/fetch`) for focused deployments.
+ * the per-tool registration helpers (`applyWebSearchTool`, `applyWebFetchTool`).
  *
  * The package owns model-facing concerns only — tool names, JSON schemas,
  * argument validation, prompt sections, result-cap constants, result formatting,