feat(unicode,datastruct): port Unicode tables and data structures

ghostty-unicode: Ghostty computes codepoint properties with the uucode
Zig package (v0.2.0, Unicode 17.0.0). There is no Rust equivalent, so
a trimmed UCD set is vendored in ucd/ and build.rs re-implements
uucode's derivations: cell width rules incl. Ghostty's overrides for
emoji modifiers and Prepend, grapheme break classes with the
compile-time grapheme_break state table, the is_symbol set, and emoji
presentation. Lookups are three array indexes per codepoint. Validated
against the official GraphemeBreakTest.txt.

ghostty-datastruct: split_tree (used for GTK splits; f16 ratios so
rounding and debug diagrams match Zig), circ_buf, lru, cache_table,
blocking_queue, segmented_pool, message_data, comparison,
array_list_collection. intrusive_linked_list is not needed (lru is
index based). lru now reports the evicted (old) key, Zig reported the
new key, which appears to be a bug.

Not yet covered: case_folding_full (needed by input bindings).

Test Plan:
- cargo test -p ghostty-unicode (16) -p ghostty-datastruct (88)
- cargo clippy for both crates with -D warnings

crates/ghostty-datastruct/src/lib.rs

@@ -1 +1,40 @@
-//! ghostty-datastruct: see docs/rewrite/ARCHITECTURE.md for the module map.
+//! The datastruct package contains data structures or anything closely
+//! related to data structures. Port of `src/datastruct/*`.
+//!
+//! `intrusive_linked_list.zig` is intentionally not ported: its only user
+//! (`lru.zig`) is implemented with an index-based list here. See
+//! `docs/rewrite/notes/ghostty-datastruct.md`.
+
+#![cfg_attr(
+    test,
+    allow(
+        clippy::unwrap_used,
+        clippy::float_cmp,
+        clippy::assert_is_empty,
+        clippy::redundant_closure_for_method_calls
+    )
+)]
+
+pub mod array_list_collection;
+pub mod blocking_queue;
+pub mod cache_table;
+pub mod circ_buf;
+pub mod comparison;
+pub mod lru;
+pub mod message_data;
+pub mod segmented_pool;
+pub mod split_tree;
+
+pub use array_list_collection::ArrayListCollection;
+pub use blocking_queue::BlockingQueue;
+pub use cache_table::CacheTable;
+pub use circ_buf::CircBuf;
+pub use message_data::MessageData;
+pub use segmented_pool::SegmentedPool;
+pub use split_tree::SplitTree;
+
+/// Stand-in for Zig's `Allocator.Error.OutOfMemory`, returned where a fixed
+/// capacity structure cannot accept more data.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, thiserror::Error)]
+#[error("out of memory")]
+pub struct OutOfMemory;