docs: sync shell/keybinding docs with the rest of the branch

Update the interactive-shell README and keybindings reference for changes
made after the initial docs commit: no scheduled GC (manual only),
NO_TMUX escape hatch, default-terminal tmux-256color + truecolor, the
JetBrainsMono Nerd Font (new Fonts section + iTerm2 caveat), the
UseKeychain IgnoreUnknown guard, and the vim-tmux-navigator (Ctrl-hjkl) +
resurrect save/restore tmux bindings.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -34,10 +34,16 @@ jobs:
       # Evaluate (not build) each host's toplevel so eval errors fail CI cheaply.
       # aarch64 / darwin hosts evaluate fine on an x86_64 runner; only building
       # would need emulation, which we deliberately avoid here.
+      #
+      # Host lists are discovered from the flake (attrNames of
+      # nixos/darwinConfigurations) rather than hard-coded, so adding or removing
+      # a host needs no change to this workflow.
       - name: Evaluate NixOS host configurations
         run: |
           set -euo pipefail
-          for host in lyrathorpe-mbp lyrathorpe-x1c emmathorpe-edaas; do
+          hosts=$(nix eval --raw '.#nixosConfigurations' \
+            --apply 'cfgs: builtins.concatStringsSep "\n" (builtins.attrNames cfgs)')
+          for host in $hosts; do
             echo "::group::eval $host"
             nix eval --raw ".#nixosConfigurations.$host.config.system.build.toplevel.drvPath"
             echo
@@ -47,7 +53,9 @@ jobs:
       - name: Evaluate Darwin host configurations
         run: |
           set -euo pipefail
-          for host in lyrathorpe-mac; do
+          hosts=$(nix eval --raw '.#darwinConfigurations' \
+            --apply 'cfgs: builtins.concatStringsSep "\n" (builtins.attrNames cfgs)')
+          for host in $hosts; do
             echo "::group::eval $host"
             nix eval --raw ".#darwinConfigurations.$host.config.system.build.toplevel.drvPath"
             echo