feat(web_search): add olostep provider

Adds Olostep (https://www.olostep.com) as an optional web_search backend
using the official olostep Python SDK (client.answers.create()).

Changes:
- pyproject.toml: adds olostep>=0.1.0 optional dependency
- schema.py: adds olostep to provider comment in WebSearchConfig
- web.py: adds _search_olostep() with lazy import and provider branching
- docs/configuration.md: documents Olostep setup under web search config
- tests: unit tests for the new provider

Backward compatible: existing users see no behavior change unless they
opt into provider: "olostep". No hard dependency at runtime path.

Co-authored-by: umerkay <umerkk164@gmail.com>

docs/configuration.md

@@ -546,6 +546,7 @@ By default, web search uses `duckduckgo`, and it works out of the box without an
 | `tavily` | `apiKey` | `TAVILY_API_KEY` | No |
 | `jina` | `apiKey` | `JINA_API_KEY` | Free tier (10M tokens) |
 | `kagi` | `apiKey` | `KAGI_API_KEY` | No |
+| `olostep` | `apiKey` | `OLOSTEP_API_KEY` | No |
 | `searxng` | `baseUrl` | `SEARXNG_BASE_URL` | Yes (self-hosted) |
 | `duckduckgo` (default) | — | — | Yes |
 
@@ -605,6 +606,22 @@ By default, web search uses `duckduckgo`, and it works out of the box without an
 }
 ```
 
+**Olostep:**
+```json
+{
+  "tools": {
+    "web": {
+      "search": {
+        "provider": "olostep",
+        "apiKey": "YOUR_OLOSTEP_API_KEY"
+      }
+    }
+  }
+}
+```
+
+You can also set `OLOSTEP_API_KEY` in the environment instead of storing it in config.
+
 **SearXNG** (self-hosted, no API key needed):
 ```json
 {