refactor(shell): modularize shell config into per-shell profiles and conf.d

Split bash config into dedicated aliases and profile files. Extract
fish shell init from config.fish into composable conf.d fragments
(setup, environment, ssh-auth-sock). Remove the generic profile in
favor of the bash-specific one. Add a static SSH_AUTH_SOCK symlink
so tmux sessions always see the current socket regardless of which
shell spawned them.

config/fish/conf.d/00-setup.fish

@@ -0,0 +1,20 @@
+if command -q mise
+    mise activate fish | source
+end
+
+if command -q direnv
+    direnv hook fish | source
+end
+
+if command -q zoxide;
+    zoxide init fish | source
+end
+
+if command -q fzf
+   fzf --fish | source
+end
+
+if command -q jj
+    jj util completion fish | source
+end
+

config/fish/conf.d/01-environment.fish

@@ -0,0 +1,11 @@
+fish_add_path "$HOME/.local/bin"
+fish_add_path "$HOME/.cargo/bin"
+
+set -gx npm_config_prefix "$HOME/.local"
+
+if command -q nvim 
+    set -gx EDITOR nvim
+end
+
+set -gx VISUAL $EDITOR
+

config/fish/conf.d/02-ssh-auth-sock.fish

@@ -0,0 +1,9 @@
+# Create a predictable symlink to the current SSH auth socket.
+# tmux forces SSH_AUTH_SOCK to ~/.ssh/ssh_auth_sock globally
+# (see config/tmux/tmux.conf), so this symlink must exist for every
+# interactive shell -- not just bash login shells.
+set -l auth_sock "$HOME/.ssh/ssh_auth_sock"
+if set -q SSH_AUTH_SOCK; and test "$SSH_AUTH_SOCK" != "$auth_sock"; and test -S "$SSH_AUTH_SOCK"
+    mkdir -p "$HOME/.ssh"
+    ln -sf "$SSH_AUTH_SOCK" "$auth_sock"
+end

config/fish/config.fish

@@ -12,27 +12,6 @@ if status is-interactive
     fish_config prompt choose default
     fish_hybrid_key_bindings
 
-    fish_add_path "$HOME/.local/bin"
-    fish_add_path "$HOME/.cargo/bin"
-
-    set -gx npm_config_prefix "$HOME/.local"
-
-    if command -q mise
-       /usr/bin/mise activate fish | source
-    end
-
-    if command -q direnv
-       /usr/bin/direnv hook fish | source
-    end
-
-    if command -q zoxide
-       /usr/bin/zoxide init fish | source
-    end
-
-    if command -q fzf
-       /usr/bin/fzf --fish | source
-    end
-
     command -q nmcli && alias nmlist "nmcli device wifi list"
 
     if command -q tree 
@@ -51,7 +30,6 @@ if status is-interactive
     command -q zero.js && alias zero 'zero.js'
 
     if command -q nvim 
-        set -gx EDITOR nvim
         alias oo "cd $SECOND_BRAIN"
         alias on "nvim '+Obsidian new'"
         alias os "nvim '+Obsidian search'"
@@ -83,8 +61,6 @@ if status is-interactive
     command -q bat && alias cat "bat"
     command -q git && alias g git
 
-    set -gx VISUAL $EDITOR
-
     if command -q jj
         /usr/bin/jj util completion fish | source
     end