feat(displays): hotplug auto-switch for display profiles (item 15b)

nomarchy-display-profile gains `match <outputs>`: an exact set match
wins, else the largest profile whose named outputs are all connected;
any tie prints nothing — the watcher must never flap between ambiguous
layouts. nomarchy-display-profile-watch (exec-once when profiles are
declared, the keyboard-watcher poll pattern — session units race
Hyprland IPC on relogin) reacts to output-set CHANGES only, reads
settings.displayProfileAuto from the live state each time (the menu's
new Auto-switch row toggles it instantly, no rebuild), and applies via
the tool — so an auto-pick persists a concrete profile that the next
rebuild bakes. A separate boolean rather than an "auto" pseudo-profile
for exactly that bake semantics.

Verified: V0 (flake check); V1 — a scratch 4-profile downstream builds;
tool + watcher pass bash -n; the match matrix exercised end-to-end:
three exact picks, an unambiguous-superset pick, a tie -> none, a
no-fit -> none; the watcher is exec-once'd in the rendered config; the
menu renders the Auto-switch row. Remains: V3 real dock/undock
(HARDWARE-QUEUE, rides the slice-a entry). Slice c (workspace binding)
stays, tagged optional.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -228,7 +228,7 @@ two tables below are split along exactly that line.
 | `nomarchy.viewers.enable` | `true` | Document/image viewers: zathura (Stylix-themed PDF) + imv |
 | `nomarchy.mime.enable` | `true` | Default "open with" associations (PDF/image/video/text/browser/directory); entries for apps you removed are skipped, so it degrades with the suite |
 | `nomarchy.monitors` | `[]` | Declarative per-output layout → Hyprland `monitor` rules (applied on hotplug); `,preferred,auto,1` wildcard kept as fallback |
-| `nomarchy.displayProfiles` | `{}` | Named layouts for the same outputs (docked/undocked/…), switched from System › Display › Profiles: instant via hyprctl, persisted in-flake (`settings.displayProfile`), baked over `nomarchy.monitors` at the next rebuild |
+| `nomarchy.displayProfiles` | `{}` | Named layouts for the same outputs (docked/undocked/…), switched from System › Display › Profiles: instant via hyprctl, persisted in-flake (`settings.displayProfile`), baked over `nomarchy.monitors` at the next rebuild. The menu's Auto-switch row (`settings.displayProfileAuto`) makes plugging/unplugging outputs apply the matching profile automatically |
 | `nomarchy.themesDir` | Nomarchy's `themes/` | Where per-theme app overrides are probed |
 | `nomarchy.package` | overlay's `nomarchy-theme-sync` | The theme/state tool package, overridable if you fork it |