chore: scaffold Cargo workspace for the Ghostty rewrite

Start of the full Rust rewrite of Ghostty 1.3.1 (reference source in
../ghostty). Sets up a workspace whose crates mirror Ghostty's Zig modules
(vt, unicode, datastruct, os, input, config, terminal, font, renderer,
termio, core, apprt-gtk) so porting work can proceed in parallel per crate.

Also adds:
- docs/rewrite/{ARCHITECTURE,PLAN,STATUS,AGENT_GUIDE}.md: crate map, core
  design decisions (safe Rust, slab-based PageList, logical capacity
  accounting), phased plan, progress tracker, and porting rules.
- Workspace clippy config relaxing pedantic lints that are pure noise for
  low-level terminal code (casts, long functions).
- Shared vt types needed by several work packages up front: kitty
  keyboard flags (kitty/key.rs) and the CSI separator bitset (SepList).

Test Plan:
- cargo test -p ghostty-vt (3 tests pass)
- cargo clippy -p ghostty-vt --all-targets -- -D warnings

crates/ghostty-vt/src/parser.rs

@@ -0,0 +1,52 @@
+//! VT-series parser for escape and control sequences
+//! (ZIG/src/terminal/Parser.zig).
+//!
+//! NOTE(W1): this file is owned by work package W1. `MAX_PARAMS` and
+//! `SepList` were pre-created by the orchestrator because `sgr` (W2)
+//! depends on them; keep their API stable.
+
+/// Maximum number of CSI parameters. This is a const in Ghostty so we
+/// match it.
+pub const MAX_PARAMS: usize = 24;
+
+/// Bitset of length `MAX_PARAMS` marking which parameters were followed by
+/// a colon (`:`) separator rather than a semicolon (`;`). Bit `i` set means
+/// the separator *after* param `i` was a colon.
+/// Equivalent to Zig's `std.StaticBitSet(MAX_PARAMS)`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Hash)]
+pub struct SepList(u32);
+
+impl SepList {
+    /// An empty set (all separators are semicolons).
+    pub const fn init_empty() -> Self {
+        Self(0)
+    }
+
+    /// Whether bit `i` is set (separator after param `i` is a colon).
+    pub fn is_set(&self, i: usize) -> bool {
+        debug_assert!(i < MAX_PARAMS);
+        self.0 & (1 << i) != 0
+    }
+
+    /// Set bit `i`.
+    pub fn set(&mut self, i: usize) {
+        debug_assert!(i < MAX_PARAMS);
+        self.0 |= 1 << i;
+    }
+
+    /// Clear bit `i`.
+    pub fn unset(&mut self, i: usize) {
+        debug_assert!(i < MAX_PARAMS);
+        self.0 &= !(1 << i);
+    }
+
+    /// Number of set bits.
+    pub fn count(&self) -> usize {
+        self.0.count_ones() as usize
+    }
+
+    /// Raw mask.
+    pub fn mask(&self) -> u32 {
+        self.0
+    }
+}