PCO Plan 1.9.0: a Song Key tile, and AbleSet-shaped section chips

**Song Key**, a third entry in the ＋ picker: the key of the item
ProPresenter has live, as large as the tile allows. It is set as a note —
B♭, F♯m rather than Bb and F#m — with the song's name and the next keyed
song under it. All three are tile settings: the colour, the name and the
next key. There is no new connection; it reads the same streamed state the
Plan tile does.

The accidental and the quality sit on the same line as the letter. Raising
the accidental read as two stacked characters at tile sizes, which is worse
than plain at a glance from the back of a room.

When the ProPresenter feed that picks the item goes away the key stays up —
the band still needs it — but faded, and the tile's dot says it is the last
item rather than the current one.

**The section chips** on the Plan tile's current item are rounded squares
now, with the tinted ground and transparent border the AbleSet module gives
its own section pills, so the two read as one family. The chip playing keeps
its own ground so its progress fills against the chip rather than against
the row behind it.

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

README.md

@@ -323,8 +323,9 @@ below. Nothing is installed without someone clicking.
   session (Start ProdDash.command) and approve the one-time prompt; a server
   started over SSH or by bare launchd silently captures zeros. (Engine
   self-test: `node modules/propresenter-timers/ltc.selftest.js`.)
-- **PCO Plan** — Planning Center Services, as two tiles in the ＋ picker:
-  **Plan** (the order of service) and **Teams** (who is scheduled).
+- **PCO Plan** — Planning Center Services, as three tiles in the ＋ picker:
+  **Plan** (the order of service), **Teams** (who is scheduled) and **Song
+  Key** (the key of the item on screen).
 
   **Plan** shows every
   plan item with its scheduled start time, length, type, song key,
@@ -355,6 +356,12 @@ below. Nothing is installed without someone clicking.
   is switched off, or it has no host — nothing to turn off and nothing to
   explain.
 
+  **Song Key** is one value, as large as the tile allows: the key of the item
+  ProPresenter has live, set as a note (B♭, F♯m), with the song's name and the
+  next key under it — both switches, as is the colour. When the feed that
+  picks the item is gone the key stays up, faded, and the tile's dot says so
+  rather than pretending to be current.
+
   **Teams** shows the same plan's team and position assignments — each team
   as a band of its people, with their photo (fetched through ProdDash, never
   by the browser; initials when Planning Center has none) and a dot for