Overhaul command palette UX

Six-phase sweep: section headers (Focused / Open / Spawn / Quit) with
header-skip cursor; chip strip mirroring sw/sp/k macros, driven by
Tab; unified Spawn verbs across agent / process / terminal / custom;
dropped duplicate global Close list in favor of Ctrl-X inline close
on a Switch row plus the [Close] chip; scored matching (prefix >
word-boundary > substring > fuzzy) with matched-char highlighting;
title bar surfaces focus subject; rename forms split long subject
onto its own row; new Alt-1..9 quick-pick, Home/End, ? help overlay,
and Ctrl-R relaunch toggle inside the spawn-process form. Scroll
indicator and cursor/total counter round out the footer.

CHANGELOG.md

@@ -6,6 +6,46 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Changed
+- Command palette UX overhaul. The single flat list grew section
+  bands (`── Focused ──`, `── Open ──`, `── Spawn ──`, `── Quit ──`)
+  so the rows are scannable at a glance; cursor navigation skips
+  the dim header rows transparently. A chip strip — `[All] Open
+  Spawn Close` — sits below the query line and tracks the active
+  macro filter; `Tab` / `Shift-Tab` cycle through the chips, and
+  the typed-prefix macros (`sw `, `sp `, `k `) still work and now
+  collapse the whole prefix on a single backspace instead of
+  leaving a stray `sw` behind. The title bar surfaces the current
+  focus subject (`on: <child>` / `pad: <name>`) so the user knows
+  which Focused row is targeting what. The duplicate global Close
+  list is gone — close is reachable via the Focused-section action,
+  the `k ` macro / `[Close]` chip, or the new `Ctrl-X` inline close
+  on a Switch row. The "(current)" marker on the focused Switch row
+  became a leading `▶`. The empty-state hint now reads `no matches
+  · ⌫ to widen` instead of bare `no matches`. The middle divider
+  shows a `▼ N more` / `▲ N above` scroll indicator when the list
+  overflows, and the footer carries a `cursor/total` counter.
+- Spawn verbs are unified on **Spawn**: `Run process: …` →
+  `Spawn process: …`, `New Terminal` → `Spawn terminal`, and the
+  freeform-form row is now `Spawn process… (custom)` so the
+  trailing ellipsis still signals it opens a form.
+- Filtering switched from binary fuzzy-include to scored ranking.
+  Prefix matches beat word-boundary matches beat substring matches
+  beat scattered-fuzzy matches; ties fall back to section order so
+  a Focused-section hit always outranks an equally tight Spawn
+  hit. The matched characters in the rendered label render in
+  accent+bold so the user can see why a row matched.
+- Rename forms split the long subject (`scratchpad:
+  some-really-long-name.md`) onto its own dim row above the input
+  so the title bar no longer truncates with an ellipsis when the
+  subject name is wide.
+- New palette accelerators: `Alt-1` … `Alt-9` quick-pick the Nth
+  visible row, `Home` / `End` jump to first / last selectable row,
+  `?` (with empty query) opens an inline keybinding cheat-sheet
+  which any further keystroke dismisses, and `Ctrl-R` inside the
+  Spawn-process form toggles "Relaunch on exit" without leaving
+  the command field.
+
 ### Fixed
 - Typing into a focused child while its emulator viewport is
   scrolled up into scrollback history now auto-snaps the viewport