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

Cargo.lock

@@ -2,6 +2,102 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "ghostty-apprt-gtk"
+version = "0.1.0"
+dependencies = [
+ "ghostty-config",
+ "ghostty-core",
+ "ghostty-input",
+]
+
+[[package]]
+name = "ghostty-config"
+version = "0.1.0"
+dependencies = [
+ "ghostty-input",
+ "ghostty-os",
+ "ghostty-vt",
+]
+
+[[package]]
+name = "ghostty-core"
+version = "0.1.0"
+dependencies = [
+ "ghostty-config",
+ "ghostty-datastruct",
+ "ghostty-font",
+ "ghostty-input",
+ "ghostty-os",
+ "ghostty-renderer",
+ "ghostty-terminal",
+ "ghostty-termio",
+]
+
+[[package]]
+name = "ghostty-datastruct"
+version = "0.1.0"
+
+[[package]]
+name = "ghostty-font"
+version = "0.1.0"
+dependencies = [
+ "ghostty-config",
+ "ghostty-terminal",
+ "ghostty-unicode",
+]
+
+[[package]]
+name = "ghostty-input"
+version = "0.1.0"
+dependencies = [
+ "ghostty-vt",
+]
+
+[[package]]
+name = "ghostty-os"
+version = "0.1.0"
+
+[[package]]
+name = "ghostty-renderer"
+version = "0.1.0"
+dependencies = [
+ "ghostty-config",
+ "ghostty-font",
+ "ghostty-terminal",
+]
+
 [[package]]
 name = "ghostty-rs"
 version = "0.1.0"
+dependencies = [
+ "ghostty-apprt-gtk",
+ "ghostty-config",
+ "ghostty-core",
+]
+
+[[package]]
+name = "ghostty-terminal"
+version = "0.1.0"
+dependencies = [
+ "ghostty-datastruct",
+ "ghostty-unicode",
+ "ghostty-vt",
+]
+
+[[package]]
+name = "ghostty-termio"
+version = "0.1.0"
+dependencies = [
+ "ghostty-config",
+ "ghostty-os",
+ "ghostty-terminal",
+]
+
+[[package]]
+name = "ghostty-unicode"
+version = "0.1.0"
+
+[[package]]
+name = "ghostty-vt"
+version = "0.1.0"