Rust core: YAML grid config, navigation state machine, evdev input

Replaces the three shell scripts' logic with one binary. tmux stays the
pane engine; src/session/ is the only module that knows that.

The grid model: coordinates are sparse ordinals, so only their sort order
matters and a socktop group is one cell however many hosts it holds.
Horizontal movement walks a cell's sub-sequence (tiled overview, then each
host zoomed) and leaves only after the last one; entry direction decides
whether you land on the first or last sub-screen. Vertical movement returns
to where you were in that row, and snaps to the nearest column only on the
first visit.

Notable details found while building:

* Unquoted "at: 0x0" is hexadecimal 0 to YAML, and "1x0" is not valid hex,
  so only the row-0 entries would break. Deserialization catches the integer
  case and names the fix.
* Panes are addressed by tmux id, never index, and each command is wrapped
  so the pane outlives it. v1's remain-on-exit cannot do this: it is a
  per-window option that new windows do not inherit, so a monitor that exits
  during construction destroys its window and the next split fails with
  "no current target". Now a dead monitor stays on screen with its status.
* Contact-count averaging, not summing: a panel reporting one finger as
  three contacts must not look like three times the travel.
* Movement subcommands wait for the move to happen and report where they
  landed, so they are scriptable rather than fire-and-forget.

36 tests: the grid model, the gesture classifier and an end-to-end pass
against a real tmux server.

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

Cargo.toml

@@ -0,0 +1,55 @@
+[package]
+name = "socktop-swipe"
+version = "2.0.0-dev"
+edition = "2021"
+rust-version = "1.82"
+description = "Swipe-to-zoom touchscreen navigation for a wall-mounted socktop dashboard"
+repository = "https://gt.wittyoneoff.com/jason/socktop-swipe"
+license = "Apache-2.0"
+readme = "README.md"
+keywords = ["tui", "touchscreen", "tmux", "dashboard", "socktop"]
+categories = ["command-line-utilities"]
+
+[dependencies]
+anyhow = "1"
+clap = { version = "4", features = ["derive"] }
+evdev = "0.12"
+serde = { version = "1", features = ["derive"] }
+serde_yaml = "0.9"
+shell-words = "1"
+
+[profile.release]
+opt-level = "s"
+lto = true
+codegen-units = 1
+strip = true
+panic = "abort"
+
+# `cargo deb` produces a package with these paths. Not used yet -- see
+# notes/PLAN-v2.md, distribution is source-only for v2.0.
+[package.metadata.deb]
+maintainer = "Jason Witty"
+depends = "tmux"
+recommends = "alacritty"
+extended-description = """\
+Drives a grid of terminal dashboards on a touchscreen. Swipe between socktop \
+hosts, an Uptime Kuma status page, a unifly UniFi TUI or any command you like. \
+Reads the touch panel directly via evdev and lays the screens out with tmux."""
+assets = [
+    ["target/release/socktop-swipe", "usr/bin/", "755"],
+    ["config.example.yaml", "usr/share/doc/socktop-swipe/", "644"],
+    ["README.md", "usr/share/doc/socktop-swipe/", "644"],
+    ["packaging/70-socktop-swipe.rules", "lib/udev/rules.d/", "644"],
+]
+
+[lib]
+name = "socktop_swipe"
+path = "src/lib.rs"
+
+[[bin]]
+name = "socktop-swipe"
+path = "src/main.rs"
+
+[dev-dependencies]
+shell-words = "1"
+serde_yaml = "0.9"