chore(checksums): refresh mcp_agent_mail installer hash

The mcp_agent_mail_rust installer landed several patches over the past
day (URL-refetch in 2ba7c0f, --no-migrate skip-marker in earlier work)
that changed install.sh content but not the checksums.yaml entry. The
auto-generator picked up the new hash; checking it in keeps the curl-bash
install path verifiable for new users.

- checksums.yaml: regenerate. The mcp_agent_mail entry's sha256 moves
  from daef5c37e061174bdbba87cea4fcc39ef4045f00090d154911b43c5d87d0ea6a
  to 40184fafa6edf9305eee33e46b4485336f58daf960ef671344003f8928a28828,
  matching the current main of mcp_agent_mail_rust. The auto-generator
  also bumps the file header timestamp and trims the trailing blank
  line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Dicklesworthstone

checksums.yaml

@@ -1,4 +1,4 @@
-# checksums.yaml - Auto-generated 2026-05-03T21:48:42-04:00
+# checksums.yaml - Auto-generated 2026-05-04T00:40:00-04:00
 # Run: ./scripts/lib/security.sh --update-checksums
 
 installers:
@@ -80,7 +80,7 @@ installers:
 
   mcp_agent_mail:
     url: "https://raw.githubusercontent.com/Dicklesworthstone/mcp_agent_mail_rust/main/install.sh"
-    sha256: "daef5c37e061174bdbba87cea4fcc39ef4045f00090d154911b43c5d87d0ea6a"
+    sha256: "40184fafa6edf9305eee33e46b4485336f58daf960ef671344003f8928a28828"
 
   mdwb:
     url: "https://raw.githubusercontent.com/Dicklesworthstone/markdown_web_browser/main/install.sh"
@@ -165,4 +165,3 @@ installers:
   zoxide:
     url: "https://raw.githubusercontent.com/ajeetdsouza/zoxide/main/install.sh"
     sha256: "0c25aed6cce9d56ee0596c9a5df8cbe99ffd0f7a7054de0262234dd268b61404"
-