Fix: Require edit_post capability for raw content in docs search

[iftakharul-islam]

Fixes weDevsOfficial/wedocs-pro#453

Problem

GET /wp/v2/docs/search is public (permission_callback => '__return_true'). When a request passed context=edit, prepare_item_for_response() added title.raw and content.raw without any capability check. A guest could read the full body of password-protected docs without the password.

Fix

• prepare_item_for_response() adds raw fields only when current_user_can( 'edit_post', $doc->ID ). Covers the search route and the parents route, which share this method.
• The search route declares a context arg (view / embed / edit, default view), so unknown values are rejected with rest_invalid_param.

Logged-in editors still get raw fields with context=edit, so nothing changes for the admin UI.

Proof

Tested on WordPress Playground (WP latest, PHP 8.3) with one published password-protected doc (body SECRET-BODY-12345) and one public doc.

Request	Before (develop / 2.6.0)	After
Guest, context=view	no raw, no leak	no raw, no leak
Guest, context=edit	raw returned, secret leaked	no raw, no leak
Guest, context=bogus	ignored	rest_invalid_param
Editor, context=edit	raw returned	raw returned

=== BEFORE (origin/develop, 2.6.0) ===
guest  context=view  | secret_leaked=no  | Public Doc=no-raw,Protected: Protected Doc=no-raw
guest  context=edit  | secret_leaked=YES | Public Doc=raw,Protected: Protected Doc=raw
guest  context=bogus | secret_leaked=no  | Public Doc=no-raw,Protected: Protected Doc=no-raw
editor context=edit  | secret_leaked=YES | Public Doc=raw,Protected: Protected Doc=raw
=== AFTER (fix branch) ===
guest  context=view  | secret_leaked=no  | Public Doc=no-raw,Protected: Protected Doc=no-raw
guest  context=edit  | secret_leaked=no  | Public Doc=no-raw,Protected: Protected Doc=no-raw
guest  context=bogus | secret_leaked=no  | error:rest_invalid_param
editor context=edit  | secret_leaked=YES | Public Doc=raw,Protected: Protected Doc=raw

The editor row returning the body is expected: editors are allowed to read raw content.