Split the client into modules, and clear out what iteration left behind

main.rs had grown to 1290 lines holding everything: the CLI, the client
state, the capture engine, the drawing, the input handling and twelve
Dispatch impls. It is now orchestration only, and the concerns live where
you would look for them — cli, app, capture, overlay — with the module
docs saying what each owns. No behaviour changed; the code moved.

Iterating in response to review left residue, now gone:

- Tile::handle was only ever written. Dropping a wayland-rs proxy does
  not destroy the object, so nothing needed it held.
- Tile::failed likewise: an earlier captures_settled() read it, and
  `settled` is what everything waits on now.
- A blanket #[allow(dead_code)] on Tile hid both of those. Fields are
  pub(crate) rather than pub so the lint keeps working.
- Tile's doc comment had drifted onto the Format enum during a patch.
- Three consecutive `if args.verbose` blocks became describe() and
  report(), and the loose ticks/releases/starved/pool_bytes counters
  became one Stats. `releases` went: frames already imply it.
- quit + quit_why + activate became one Ending enum and picked, so
  "closed by the compositor" is a state rather than a string.
- App::new took seven positional arguments, two of them bare integers in
  a row; the four that always travel together are now Settings.
- sway::scale and the display listing each called get_outputs; one call
  does both.
- scaled(rect, n) became Rect::scaled(n), and Format lives with Target
  where render() dispatches on it.

README had drifted too: the usage line still advertised --print, which
no longer exists, and omitted --format and --no-outputs. Its flag list is
now checked against --help, the memory figures are re-measured, and there
is a source layout for anyone arriving cold.

README.md

@@ -35,25 +35,26 @@ is the one thing the rofi version had that this doesn't — see the roadmap.
 ## Usage
 
 ```
-wl-pick [--print] [--verbose] [--hide-labels] [--font FAMILY] [--font-size PX]
-       [--live all|current|none] [--fps N] [--timeout SECS]
+wl-pick [--format tsv|json|portal] [--live all|current|none] [--fps N]
+        [--no-outputs] [--hide-labels] [--font FAMILY] [--font-size PX]
+        [--timeout SECS] [--verbose]
 ```
 
-- `--verbose` prints phase timings and how many windows were captured
+- `--format tsv|json|portal` how to report the pick (default `tsv`)
+- `--live all|current|none` which tiles keep updating (default `all`; displays
+  are always a single snapshot)
+- `--fps N` cap on live updates per tile per second (default 12)
+- `--no-outputs` windows only; displays are included as tiles by default
 - `--hide-labels` draws an icon-only grid
 - `--font FAMILY` label font family (default `Berkeley Mono`)
 - `--font-size PX` label size in logical px
-- `--live all|current|none` which tiles keep updating (default `all`)
-- `--fps N` cap on updates per tile per second (default 12)
-- `--timeout SECS` exits after a deadline (an escape hatch: the overlay takes an
-  exclusive keyboard grab)
+- `--timeout SECS` exits after a deadline, in case the keyboard grab ever traps
+  you
+- `--verbose` phase timings, the tile list, and capture stats
 
-wl-pick is a chooser: it reports what you picked and leaves acting on it to the
-caller. The pick goes to stdout, nothing does if you cancel, and the exit status
-is 0 for a pick and 1 for a cancel.
-
-wl-pick never acts on the choice — it has no idea what you want to do with it.
-Focusing on sway looks like this:
+wl-pick is a chooser: the pick goes to stdout, nothing does if you cancel, and
+the exit status is 0 for a pick and 1 for a cancel. It never acts on the choice —
+it has no idea what you want to do with it. Focusing on sway looks like this:
 
 ```sh
 #!/usr/bin/env bash
@@ -121,9 +122,9 @@ from being expensive:
   back, so the slot on screen is usually free too — waiting for it to stop being
   displayed instead deadlocks after two frames.
 
-The cost is memory and bandwidth: two full-resolution buffers per window (110 MB
-of shm for ten windows on this display, versus 55 MB with `--live none`) and a
-readback per refreshed frame. `--live current` refreshes only the selected tile,
+The cost is memory and bandwidth: two full-resolution buffers per window (138 MB
+of shm for eight windows and a display here, against 83 MB with `--live none`)
+and a readback per refreshed frame. `--live current` refreshes only the selected tile,
 which is much cheaper and still reads as alive.
 
 ## Look
@@ -131,8 +132,8 @@ which is much cheaper and still reads as alive.
 Colours, font metrics and grid geometry come from the rofi theme this replaces
 (gruvbox dark, a yellow selection filling the element padding, `ceil(sqrt(n))`
 columns capped at 4, 16:9 tiles, `title · app` centred underneath) and live in
-`src/theme.rs`. They will move to a config file so they can't drift from the
-`.rasi`.
+`src/theme.rs`, which is the one place to change them. They are not
+configurable at runtime beyond the font flags.
 
 The font is looked up by family name. Your own font directories are scanned
 first because they are small; the full system scan (~37ms) happens only if the
@@ -161,9 +162,24 @@ unaffected. It matters more once previews are live.
 - dmabuf capture, so the pixels never leave the GPU at all — and live previews
   stop costing a readback per frame
 
+## Source layout
+
+```
+main.rs     orchestration: list, capture, map, report the pick
+cli.rs      flags, defaults, and the help text that documents them
+sway.rs     the window list and display names, over sway's IPC socket
+target.rs   what a tile stands for, and the three output formats
+app.rs      the Wayland client state every event dispatches into
+capture.rs  capture sessions, their buffers, and the live clock
+overlay.rs  the layer surface, the drawing, and the keyboard
+theme.rs    colours, grid geometry, aspect fitting
+text.rs     label shaping on a worker thread
+shm.rs      memfd allocation and the ARGB painter
+```
+
 ## Building
 
 ```
 cargo build --release
-cargo test          # grid geometry, ellipsising, glyph output
+cargo test          # grid geometry, ellipsising, output formats, glyph output
 ```