fix: address codex review findings on web seam

- search providers (exa/perplexity/deepseek): map the parsed response
  INSIDE the parse try, so a well-formed body of the wrong shape surfaces
  as WEB_PROVIDER_ERROR instead of escaping as a raw TypeError; a WebError
  the mapper throws on purpose is re-thrown untouched
- web-fetch-local: validate numeric limits at plugin construction (positive
  finite caps; non-negative integer maxRedirects) rather than constructing a
  provider with nonsensical values
- web-fetch-local: enforce the redirect budget BEFORE resolving each hop, so
  maxRedirects:N follows exactly N redirects and an over-limit hop reports
  "exceeded the maximum" rather than misdiagnosing a cross-origin block
- drop the stale dsh-tool-web/search and /fetch path aliases (the package no
  longer declares those subpath exports)
- strip trailing EOF blank lines flagged by git diff --check

Each fix carries a regression test.

packages/web/web-search-perplexity/src/provider.ts

@@ -126,14 +126,14 @@ export class PerplexitySearchProvider implements WebSearchProvider {
       throw new WebError(message, 'WEB_PROVIDER_ERROR')
     }
 
-    let payload: PerplexityResponse
     try {
-      payload = await response.json() as PerplexityResponse
+      const payload = await response.json() as PerplexityResponse
+      return mapPerplexityResponse(request.query, payload)
     } catch (error: unknown) {
       if (isAbortError(error)) throw new WebError('Perplexity search aborted', 'WEB_ABORTED', { cause: error })
-      throw new WebError(`Perplexity returned an unparseable response body: ${String(error)}`, 'WEB_PROVIDER_ERROR', { cause: error })
+      if (error instanceof WebError) throw error
+      throw new WebError(`Perplexity returned an unprocessable response body: ${String(error)}`, 'WEB_PROVIDER_ERROR', { cause: error })
     }
-    return mapPerplexityResponse(request.query, payload)
   }
 }