Replace print CLIRenderer with differential TUI engine

Implement TUI Phase 1: a raw-mode terminal, differential render engine,
pinned input box + footer, and component model wired into the libpanto
event stream. Adds foundation modules (theme, key, component, input,
terminal), the render engine, components, and the app loop; removes the
old print CLIRenderer and driveTurn REPL from main.zig.

Also removes scratch status reports (tui-p1/, progress.md) for the now
completed work.

1 files changed, 129 insertions, 0 deletions

diff --git a/src/tui_key.zig b/src/tui_key.zig
new file mode 100644
index 0000000..e5056cd
--- /dev/null
+++ b/src/tui_key.zig
@@ -0,0 +1,129 @@
+//! Input value types for the TUI.
+//!
+//! This is the *rich* key model. The P1 decoder (`tui_input.zig`) only
+//! populates a subset of it (printable chars, enter, backspace, arrows,
+//! home/end, escape, Ctrl+C, Ctrl+D), but the model is intentionally complete
+//! so later phases (full Kitty disambiguation, key-release events, super/hyper
+//! modifiers) can populate the rest without changing the type. Components
+//! built on this model will keep compiling.
+
+const std = @import("std");
+
+/// A logical key, independent of the raw bytes that produced it.
+///
+/// `char` carries a Unicode codepoint (the printable case). All other
+/// variants are non-printable named keys. The decoder resolves the *display
+/// text* of a printable key separately into `Key.text` (so e.g. a pasted or
+/// composed grapheme can be carried verbatim), while `char` holds the single
+/// decoded codepoint.
+pub const KeyCode = union(enum) {
+    /// A printable character, as a Unicode codepoint.
+    char: u21,
+    enter,
+    escape,
+    tab,
+    backspace,
+    delete,
+    up,
+    down,
+    left,
+    right,
+    home,
+    end,
+    page_up,
+    page_down,
+    f1,
+    f2,
+    f3,
+    f4,
+    f5,
+    f6,
+    f7,
+    f8,
+    f9,
+    f10,
+    f11,
+    f12,
+};
+
+/// Modifier flags. Packed so it round-trips cheaply and compares by value.
+///
+/// `super` is Cmd/Win, `hyper` is the (rare) Hyper modifier; both are only
+/// expressible under protocols like Kitty's, so the P1 decoder leaves them
+/// false. They exist so the model can represent them later.
+pub const Mods = packed struct {
+    ctrl: bool = false,
+    alt: bool = false,
+    shift: bool = false,
+    super: bool = false,
+    hyper: bool = false,
+
+    pub const none: Mods = .{};
+
+    pub fn eql(a: Mods, b: Mods) bool {
+        return @as(u5, @bitCast(a)) == @as(u5, @bitCast(b));
+    }
+
+    pub fn any(self: Mods) bool {
+        return @as(u5, @bitCast(self)) != 0;
+    }
+};
+
+/// Press / repeat / release. Terminals that don't report key-release (most,
+/// without the Kitty protocol) only ever produce `.press`. A component opts
+/// into receiving `.release` via `Component.wantsKeyRelease`.
+pub const KeyEvent = enum {
+    press,
+    repeat,
+    release,
+};
+
+/// A fully decoded key.
+///
+/// `text` is the resolved text to insert for a printable key (UTF-8 encoding
+/// of `code.char`, or pasted text surfaced as a literal run). It is null for
+/// non-printable keys. `text`, when non-null, is borrowed from the input
+/// buffer the decoder was handed; callers must copy it if they need it to
+/// outlive that buffer.
+pub const Key = struct {
+    code: KeyCode,
+    mods: Mods = .{},
+    event: KeyEvent = .press,
+    text: ?[]const u8 = null,
+
+    /// Convenience: is this a plain (unmodified) press of `code`?
+    pub fn isPlain(self: Key, code: KeyCode) bool {
+        return self.event == .press and !self.mods.any() and std.meta.eql(self.code, code);
+    }
+
+    /// Convenience: Ctrl+<letter> press, e.g. `isCtrl('c')`. `letter` is
+    /// matched case-insensitively against the printable codepoint.
+    pub fn isCtrl(self: Key, letter: u8) bool {
+        if (self.event == .release) return false;
+        if (!self.mods.ctrl) return false;
+        return switch (self.code) {
+            .char => |cp| cp == std.ascii.toLower(@intCast(letter & 0x7f)) or
+                cp == std.ascii.toUpper(@intCast(letter & 0x7f)),
+            else => false,
+        };
+    }
+};
+
+test "Mods eql / any" {
+    try std.testing.expect(Mods.none.eql(.{}));
+    try std.testing.expect(!Mods.none.any());
+    const c: Mods = .{ .ctrl = true };
+    try std.testing.expect(c.any());
+    try std.testing.expect(!c.eql(.{ .shift = true }));
+}
+
+test "Key.isPlain / isCtrl" {
+    const a: Key = .{ .code = .{ .char = 'a' } };
+    try std.testing.expect(a.isPlain(.{ .char = 'a' }));
+    try std.testing.expect(!a.isPlain(.enter));
+
+    const ctrl_c: Key = .{ .code = .{ .char = 'c' }, .mods = .{ .ctrl = true } };
+    try std.testing.expect(ctrl_c.isCtrl('c'));
+    try std.testing.expect(ctrl_c.isCtrl('C'));
+    try std.testing.expect(!ctrl_c.isCtrl('d'));
+}