Add emoji prefix.

README.md

@@ -126,6 +126,8 @@ key.zig        GDK keyval -> libghostty-vt key mapping
 theme.zig      colors libghostty-vt has no opinion about, per scheme
 Settings.zig   preferences: model, JSON on disk
 SettingsDialog.zig    the settings page
+TabSettingsDialog.zig one tab's own settings, and the emoji picker
+emoji.zig      generated: every emoji the picker offers, and the search over them
 ```
 
 A tab is a **view**, and a view holds one or more **panes** arranged in a
@@ -325,8 +327,12 @@ in principle, but a terminal grid is small.
 - **Pane status in the tab strip**, driven by OSC 9;4, so a tab can say whether
   it is working, waiting on you, or finished and still unanswered. See
   [Agent status](#agent-status)
-- **Renaming a tab**: `Ctrl+Shift+R`, right-click or double-click a tab row.
-  A typed name pins the label; clearing it hands the label back to the panes
+- **Renaming a tab**: `Ctrl+Shift+R`, double-click a tab row, or **Rename** in
+  its right-click menu. A typed name pins the label; clearing it hands the
+  label back to the panes
+- **An emoji in place of a tab's icon**, from **Settings** in the same
+  right-click menu, picked out of the full emoji set with keyword search. See
+  [Tab settings](#tab-settings)
 - **Zooming a pane** to fill its tab and back, from the header button or
   `Ctrl+Shift+Z`. Nothing closes and nothing moves — hidden panes keep running
   and the split comes back exactly as it was. See [Zoom](#zoom)
@@ -383,6 +389,46 @@ that zoom is hiding. Closing the zoomed pane leaves zoom; a *different* pane
 closing — a background shell exiting, say — does not, since what you are looking
 at is still there.
 
+## Tab settings
+
+Right-clicking a tab row opens a small menu: **Rename**, which is the same
+one-field popover `Ctrl+Shift+R` opens, and **Settings…**, which opens a window
+belonging to that one tab. Double-clicking a row still goes straight to renaming
+— it is the thing you do far more often than the other.
+
+The window holds one setting today, **Emoji Label**: a glyph that stands in for
+the pane icon in that tab's sidebar row. It replaces the icon rather than joining
+it, since a row has one slot for "what is this tab" and the label needs the rest
+of the width. **Use the pane icon** puts the icon back.
+
+Picking one is a search box over a grid of the whole emoji set — 1906 glyphs, in
+Unicode's own order and grouping, so it reads the way any other emoji keyboard
+does. A glyph's tooltip is its name, for the ones you can't quite make out at
+grid size.
+
+Every whitespace-separated word in the query has to match, in any order, so
+`green circle` and `circle green` both land on 🟢 while `circle` alone brings back
+the whole family. Keywords are CLDR's, which is where `grin` finding 😀 comes
+from, plus the group and subgroup each glyph belongs to — `fruit`, `arrow` and
+`flags` each bring back a shelf — plus a table of synonyms for the words a
+terminal user actually types: `deploy` finds 🚀, `hotfix` finds 🩹, `docker` finds
+🐳, `rust` finds 🦀.
+
+`src/emoji.zig` is generated by `tools/gen-emoji.py` from Unicode's
+`emoji-test.txt` and CLDR's English annotations; run that rather than editing the
+table, and add to its `SYNONYMS` when a glyph should answer to a word the data
+files don't know. Two things it leaves out. Skin-tone variants, because just over
+half of Unicode's 3944 sequences are the same gesture in five tones and a grid of
+them is longer to look through rather than more complete — every base glyph is
+there. And anything newer than emoji 16.0, because colour fonts trail Unicode by
+a year or two and a glyph the font has never heard of draws as a hex-digit box,
+which in a picker reads as a bug; `--max-version` raises the cutoff once fonts
+have caught up.
+
+The choice lives on the tab and not on disk, the same as a typed name: it lasts
+as long as the tab does. Saving the tab as a layout does not carry it, since a
+layout describes an arrangement of panes rather than what a row looks like.
+
 ## Agent status
 
 Playpen is mostly used to keep several Claude Code sessions side by side, and
@@ -627,9 +673,16 @@ emit from and the client never sees it. Anything reachable only by clicking has
 to be reached another way — a keyboard shortcut, or `zig build test` if the
 thing being checked is logic rather than pixels.
 
-`zig build test` runs the unit tests, which cover layout parsing and the
-parameter/`$(...)` substitution pipeline. They are rooted at `Layouts.zig` so
-the test binary never links GTK.
+`zig build test` runs the unit tests, which cover layout parsing, the
+parameter/`$(...)` substitution pipeline, and the emoji table and its search.
+They build as two binaries, rooted at `Layouts.zig` and `emoji.zig`, so neither
+links GTK — a test binary has one root, and those are the two files worth
+testing in isolation that have nothing to do with each other.
+
+`tools/gen-emoji.py` regenerates `src/emoji.zig` from Unicode's `emoji-test.txt`
+and CLDR's annotations. It is not part of the build — its output is committed, so
+a build never needs the network — and `--check` reports whether what is committed
+is what it would write. See [Tab settings](#tab-settings).
 
 Web panes need an EGL display and the headless compositor has no GPU, so
 `shot.sh` forces the dev shell's mesa down to its software rasterizer. The mesa