## Why

The Go client's human-mode search output struct expects a nested `document` object and top-level `page`/`section` fields, but the engine API returns flat results with `title`, `doc_type`, `tags` at the result level and `page`/`section_header` inside `chunk_metadata`. This means human-mode display shows empty values for title, type, tags, page, and section.

## What Changes

- Fix the Go client search result struct to match the flat engine API response format
- Extract `page` and `section_header` from the `chunk_metadata` map instead of expecting them as top-level fields
- Human-mode output will correctly display document title, type, tags, page number, and section header

## Capabilities

### New Capabilities

(none)

### Modified Capabilities

- `go-client`: Fix search result parsing to match actual engine API response shape

## Impact

- `client/cmd/search.go` — struct definition and display logic
- No API changes, no breaking changes — this is a bug fix aligning the client with the existing API contract