feat(neomutt): add keybindings, sidebar colors, mailcap, and urlscan integration

- Remap sidebar-open from Ctrl+O to 'o' for single-key access
- Add Enter/l/h/0/$ keybindings across index, pager, and browser modes
- Add macros: O (mbsync sync), gx (urlscan link extraction), gl (flag legend)
- Add extraConfig with abort_key, mailcap_path, and auto_view for attachments
- Add mailcap for w3m/html, image/pdf/video/audio openers via xdg-open
- Add flag_legend.txt help file accessible via 'gl'
- Add home.packages for urlscan and w3m
- Add checkStatsInterval = 20

- Add sidebar colors (background, divider, ordinary, new, flagged, spool_file, highlight, indicator)
- Add prompt, progress, stripe_odd/stripe_even, and attach_headers colors
- Add index_collapsed, index_label, index_tag, and index_tags color targets
- Fix indicator to use brightblack background instead of blue for better contrast
- Extend quoted colors from 4 to 9 levels for deeply nested replies
- Change Date header color to green
- Update index_format with padding for cleaner alignment

- Add mailboxes, Expunge = Both, and notmuch virtual mailboxes to email example

1 files changed, 137 insertions, 3 deletions

diff --git a/modules/programs/neomutt/default.nix b/modules/programs/neomutt/default.nix
index 940ce9a..e489328 100644
--- a/modules/programs/neomutt/default.nix
+++ b/modules/programs/neomutt/default.nix
@@ -2,21 +2,76 @@
 {
   config,
   lib,
+  pkgs,
   ...
 }:
-
 {
   imports = [
     ./assertions.nix
     ./theme.nix
   ];
-
   config = lib.mkIf config.programs.neomutt.enable {
+    home.packages = [
+      pkgs.urlscan
+      pkgs.w3m
+    ];
+
+    xdg.configFile."neomutt/mailcap".text = ''
+      text/html; w3m -dump -T text/html '%s'; copiousoutput; nametemplate=%s.html
+      text/html; $BROWSER '%s'; nametemplate=%s.html
+      image/*; xdg-open '%s' &
+      application/pdf; xdg-open '%s'; nametemplate=%s.pdf
+      video/*; xdg-open '%s' &
+      audio/*; xdg-open '%s' &
+      application/*; xdg-open '%s' &
+    '';
+
+    xdg.configFile."neomutt/flag_legend.txt".text = ''
+      NeoMutt Index Flags
+      ===================
+
+      Message state ($flag_chars)
+        N   New       - unread, arrived since you last checked
+        O   Old       - unread, but seen in a previous session
+        D   Deleted   - marked for deletion (pending expunge)
+        d   Att-del   - has attachments marked for deletion
+        !   Flagged   - important (toggle with F)
+        *   Tagged    - selected for a bulk operation (toggle with t)
+        r   Replied   - you've replied to this message
+        S   Signed    - PGP/SMIME signed
+        P   Encrypted - PGP/SMIME encrypted
+        s   Cert      - contains a S/MIME certificate/key
+        K   PGP key   - contains a PGP public key
+        (blank)       - read, nothing else notable
+
+      Addressing ($to_chars)
+        +   To you only     - sent to you and only you
+        T   To (with others) - you're in the To: list, among others
+        C   Cc only          - you're only in the Cc: list
+        F   From you         - sent by you
+        L   Mailing list     - sent to a list you're subscribed to
+        (blank)              - not in To/Cc (e.g. Bcc, unlisted)
+
+      Press q to close.
+    '';
+
     programs.neomutt = {
       sidebar.enable = true;
       sort = "reverse-threads";
       vimKeys = true;
       unmailboxes = true;
+      checkStatsInterval = 20;
+
+      extraConfig = ''
+        # cancel any prompt/command-line entry with Esc, vim-style
+        set abort_key = "<Esc>"
+
+        # attachments: use our mailcap for dedicated openers,
+        # and auto-render html/images inline where sensible
+        set mailcap_path = "~/.config/neomutt/mailcap"
+        auto_view text/html image/png image/jpeg image/gif application/pdf
+      '';
+
       binds = [
         {
           map = [
@@ -35,13 +90,75 @@
           action = "sidebar-next";
         }
         {
+          # select the highlighted mailbox directly, no Ctrl+O needed
           map = [
             "index"
             "pager"
           ];
-          key = "\\CO";
+          key = "o";
           action = "sidebar-open";
         }
+
+        {
+          map = [ "index" ];
+          key = "<Return>";
+          action = "display-message";
+        }
+        {
+          map = [ "browser" ];
+          key = "<Return>";
+          action = "select-entry";
+        }
+        {
+          map = [ "attach" ];
+          key = "<Return>";
+          action = "view-attach";
+        }
+        {
+          map = [
+            "alias"
+            "query"
+          ];
+          key = "<Return>";
+          action = "select-entry";
+        }
+        {
+          map = [ "pager" ];
+          key = "<Return>";
+          action = "next-page";
+        }
+
+        {
+          map = [ "index" ];
+          key = "l";
+          action = "display-message";
+        }
+        {
+          map = [ "pager" ];
+          key = "h";
+          action = "exit";
+        }
+        {
+          map = [ "pager" ];
+          key = "l";
+          action = "next-unread";
+        }
+        {
+          map = [ "index" ];
+          key = "h";
+          action = "collapse-thread";
+        }
+
+        {
+          map = [ "pager" ];
+          key = "0";
+          action = "top";
+        }
+        {
+          map = [ "pager" ];
+          key = "$";
+          action = "bottom";
+        }
       ];
 
       macros = [
@@ -53,6 +170,23 @@
           key = "O";
           action = "<sync-mailbox><shell-escape>mbsync -a<enter><sync-mailbox>";
         }
+        {
+          # gx: extract links from the current message and open one, vim-netrw style
+          map = [
+            "index"
+            "pager"
+          ];
+          key = "gx";
+          action = "<pipe-message>urlscan<Enter>";
+        }
+        {
+          map = [
+            "index"
+            "pager"
+          ];
+          key = "gl";
+          action = "<shell-escape>less ~/.config/neomutt/flag_legend.txt<enter>";
+        }
       ];
     };
   };