Make version parameter explicitly required for search_symbols function

[johnkferguson]

The search_symbols function currently marks the version parameter as optional, but testing shows it doesn't work without it. To avoid hidden assumptions about which version is being used, the version parameter should be explicitly required.

Current Behavior

• Parameter is marked as optional in the schema
• Function fails with HTTP error\! status: 404 when version is omitted
• Works correctly when version is provided

Example that fails:

{
  "crateName": "std",
  "query": "Vec"
}

Example that works:

{
  "crateName": "serde", 
  "version": "1.0.219",
  "query": "Serialize"
}

Proposed Solution

Update the function schema to mark version as a required parameter. This provides clarity about which exact version is being searched and avoids any ambiguity about default version selection.

Benefits

• Eliminates confusing 404 errors
• Makes version selection explicit and intentional
• Prevents assumptions about "latest" version behavior