Enhancement: Return pagination metadata in semantic_code_search response

[kapral18]

Summary

Add totalHits to the semantic_code_search response to help agents make informed decisions about whether to paginate further or switch to other tools like map_symbols_by_query.

Current Behavior

The tool accepts page and size parameters but returns only the hits array:

// src/mcp_server/tools/semantic_code_search.ts:84-101
return {
  content: [
    {
      type: 'text',
      text: JSON.stringify(
        response.hits.hits.map((hit) => {
          const { type, language, kind, filePath, content } = hit._source;
          return { score: hit._score, type, language, kind, filePath, content };
        })
      ),
    },
  ],
};

Response shape:

[
  { "score": 0.92, "type": "code", "filePath": "...", "content": "..." },
  { "score": 0.87, "type": "code", "filePath": "...", "content": "..." }
]

Proposed Behavior

Include pagination metadata from the already-available response.hits.total:

{
  "hits": [
    { "score": 0.92, "type": "code", "filePath": "...", "content": "..." },
    { "score": 0.87, "type": "code", "filePath": "...", "content": "..." }
  ],
  "total": 142
}

Why This Helps Agents

┌────────────────────────────────────────────────────────────────────┐
│  Agent receives: { hits: [...25 items], total: 142 }               │
├────────────────────────────────────────────────────────────────────┤
│                                                                    │
│  Agent can now reason:                                             │
│                                                                    │
│  • "142 total results, I have 25 - there's more if I need it"     │
│  • "142 is a lot - maybe map_symbols_by_query is better for       │
│     exhaustive coverage"                                           │
│  • "Only 8 total results - no need to paginate"                   │
│                                                                    │
└────────────────────────────────────────────────────────────────────┘

Implementation

Minimal change in src/mcp_server/tools/semantic_code_search.ts:

// Extract total from ES response (already available)
const total = typeof response.hits.total === 'number' 
  ? response.hits.total 
  : response.hits.total?.value ?? 0;

return {
  content: [
    {
      type: 'text',
      text: JSON.stringify({
        hits: response.hits.hits.map((hit) => {
          const { type, language, kind, filePath, content } = hit._source;
          return { score: hit._score, type, language, kind, filePath, content };
        }),
        total,
      }),
    },
  ],
};

Acceptance Criteria

• Response includes total field with the total number of matching documents
• Existing hits array structure unchanged (backward compatible for agents parsing the array)