refactor: update search tool to match Obsidian CLI spec

Removed obsidian_search_with_context tool (not in CLI spec)
Updated obsidian_search to use exact CLI parameter names:
- query (required) - Search query text
- path (optional) - Limit search to folder path
- limit (optional) - Max number of files to return
- total (optional) - Return match count instead of file list
- case (optional) - Case sensitive search
- format (optional) - Output format: text or json (default: text)

Changed parameter names to match CLI:
- folder → path
- caseSensitive → case
- Added: total flag for match counts
- Removed: contextLines (not in CLI)

Files updated:
- src/tools/search.ts: Simplified to single search tool
- src/validation/schemas.ts: Updated searchSchema parameters
- manifest.json: Removed search_with_context, updated description
- tasks.md: Marked T048 as REMOVED

Total tools: 20 (was 21)
- User Story 1: 9 tools
- User Story 2: 11 tools (was 12)

Build: ✅ 0 errors
Validation: ✅ Manifest passes

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

manifest.json

@@ -72,11 +72,7 @@
     },
     {
       "name": "obsidian_search",
-      "description": "Search for notes in the vault by content. Returns matching files with optional context snippets. Supports case-sensitive search and folder filtering."
-    },
-    {
-      "name": "obsidian_search_with_context",
-      "description": "Search for notes with surrounding context. Returns matching lines with context before and after the match for better understanding."
+      "description": "Search vault for text. Returns matching files and optionally match counts. Supports path filtering, result limits, case sensitivity, and multiple output formats (text/json)."
     },
     {
       "name": "obsidian_get_backlinks",