feat(shell): curated git/nix/navigation aliases on by default

Extend the zsh shellAliases in shell.nix with a curated, on-by-default
set: navigation (.., ..., ....), a git block (g, gst, ga/gaa, gc/gcm,
gco/gsw, gb, gd/gds, gl/glg, gp/gpl, gf), a nix block (ns, nr, nfu, nfc,
nsearch, ngc), and path/reload. Same restraint as rg/fd: short where it
helps but never shadowing a real binary — the git set keeps off gs
(ghostscript), and the system/home rebuilds keep their sys-update /
home-update names rather than cryptic aliases.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -113,10 +113,14 @@ how to override it. Items marked ✓ are shipped.
   summer-day/night menu buttons now use its `U+F000` glyph with
   `font-family: Nomarchy` pinned in their CSS (Nerd Fonts also occupy
   U+F000, so the pin is required). The other themes have no logo button.
-- **Quality-of-life command aliases:** assemble a curated collection of
-  shell aliases/abbreviations for common operations (git, nix, navigation,
-  the nomarchy helpers, …), themed into the zsh shell experience
-  (`modules/home/shell.nix`). Decide scope and which to ship on by default.
+- ✓ **Quality-of-life command aliases:** a curated set ships on by default in
+  `modules/home/shell.nix` — navigation (`..`/`...`/`....`), a git block
+  (`g`, `gst`, `ga`/`gaa`, `gc`/`gcm`, `gco`/`gsw`, `gb`, `gd`/`gds`,
+  `gl`/`glg`, `gp`/`gpl`, `gf`), and a nix block (`ns`, `nr`, `nfu`, `nfc`,
+  `nsearch`, `ngc`), plus `path` and `reload`. Scope decision: short where it
+  helps but **never shadow a real binary** (same rule as rg/fd — the git block
+  deliberately avoids `gs`/ghostscript); system/home rebuilds keep their full
+  `sys-update`/`home-update` names rather than getting cryptic aliases.
 - **Theme-switch feedback:** ✓ the "rebuilding…" notification is now
   persistent (timeout 0) and replaced in place by "applied ✓" / failure
   via a synchronous tag, so a multi-minute switch never reads as a failed