feat(bin): bundle Obsidian MCP server into bin plugin

## Why

The Obsidian MCP server config was living at the repo root, making it
a repo-level concern rather than part of the plugin it belongs to.
Moving it into plugins/bin/ means the plugin is self-contained and the
server travels with it on install.

## Implementation Notes

mcpServers is declared in the Copilot manifest (plugin.json) because
Copilot requires explicit path declarations. CC auto-discovers .mcp.json
from the plugin root so no change to the CC manifest is needed.

Bumps version to 1.0.3 in both manifests.

---

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/bin/.mcp.json

@@ -0,0 +1,12 @@
+{
+  "mcpServers": {
+    "obsidian": {
+      "args": [
+        "@bitbonsai/mcpvault@latest",
+        "docs/"
+      ],
+      "command": "npx",
+      "type": "stdio"
+    }
+  }
+}