feat: share env files as encrypted links

S → f on a repo, an env file or a key in one copies a
lazysecrets://share link holding the env files, encrypted (age) with
a secret's value: whoever can read that secret can open it. The key is
share.key in the repo's .lazysecrets.yaml, else in the config, else
picked when sharing; on Azure the link pins its version. Opening one
says what it holds, decrypts when asked, and saves the files in the
clone of the repo (or a folder chosen), replacing existing ones only
when asked. lazysecrets share prints a link from the command line.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/repos.md

@@ -55,6 +55,14 @@ providers:
     exclude: ["**/testdata/**"]
 ```
 
+A repo's `.lazysecrets.yaml` can also name the secret its env files are
+[shared](links.md#sharing-env-files) with:
+
+```yaml
+share:
+  key: lazysecrets://azure/kv-team.vault.azure.net/secrets/env-share
+```
+
 ## Decrypting
 
 Listing never decrypts: SOPS encrypts values only, so keys and metadata
@@ -90,6 +98,8 @@ sops 3.8 or later.
 
 ## Links
 
+`S` → `f` shares env files as an [encrypted link](links.md#sharing-env-files).
+
 Links name the repo by its git remote, so they open in a colleague's clone
 wherever it is: