feat(coding-agent): add SSH URL support for git packages

Use hosted-git-info library for robust parsing of SSH URLs (git@host:path
and ssh://) in addition to HTTPS. SSH and HTTPS URLs for the same repo
are now properly deduplicated.

packages/coding-agent/docs/packages.md

@@ -60,13 +60,32 @@ npm:pkg
 ```
 git:github.com/user/repo@v1
 https://github.com/user/repo@v1
+git@github.com:user/repo@v1
+ssh://git@github.com/user/repo@v1
 ```
 
+- HTTPS and SSH URLs are both supported.
+- SSH URLs use your configured SSH keys automatically (respects `~/.ssh/config`).
 - Raw `https://` URLs work without the `git:` prefix.
 - Refs pin the package and skip `pi update`.
 - Cloned to `~/.pi/agent/git/<host>/<path>` (global) or `.pi/git/<host>/<path>` (project).
 - Runs `npm install` after clone or pull if `package.json` exists.
 
+**SSH examples:**
+```bash
+# Standard git@host:path format
+pi install git@github.com:user/repo
+
+# With git: prefix
+pi install git:git@github.com:user/repo
+
+# ssh:// protocol format
+pi install ssh://git@github.com/user/repo
+
+# With version ref
+pi install git@github.com:user/repo@v1.0.0
+```
+
 ### Local Paths
 
 ```