session 1 commit 4/4: message envelopes moved to pmacs-protocol

The big move that completes session 1. Wire types moved from
src/protocol.rs to pmacs-protocol/src/message.rs:

- Input event family: Key, Modifiers, KeyEvent, MouseButton, MouseKind,
  MouseEvent, FrontendEvent (and its variants — Resize, KeyEvent,
  MouseEvent, Resume, Pause, Detach, ResizeAck, CrdtOp, Viewport).
- Instance-side message family: CursorState, InstanceSignal,
  GoodbyeReason, InstanceMessage (Hello/Cursor/CellDelta/CursorByte/
  CrdtOp/BufferSnapshot/Goodbye/PresenceUpdate + the SemanticFrame
  variants).
- SelectionSnapshot.
- SemanticFrame family components: StyleSpan, StyleSegment,
  DecorationKind, Decoration, DecorationSegment, AdornmentPlacement,
  AdornmentContent, InlineAdornment, BlockAdornment, ResourceBody.
- Handshake: PROTOCOL_VERSION, SUPPORTED_PROTOCOL_VERSIONS,
  is_supported_protocol_version, InstanceIdentity, InstanceCapabilities,
  FrontendCapabilities, NegotiatedCapabilities, negotiate_capabilities,
  Hello, AttachRequest.

What stays in src/protocol.rs:
- AttachTarget / AttachError / AttachTargetParseError /
  AttachTargetValidationError / AttachTargetError / AttachmentHandle
  (CLI / binding internals, not wire).
- crossterm_translate submodule (the crossterm ↔ pmacs-protocol-types
  translation layer; sits at the binding boundary, not on the wire).
- Existing tests (wire-format roundtrip + AttachTarget + crossterm
  translation), unchanged — they reach the moved types through the
  'pub use pmacs_protocol::*' re-export.

Mechanical rewrites inside the moved chunk: crate::buffer::BufferId →
crate::BufferId, crate::rope::Position → crate::Position,
crate::rope::CrdtOp → crate::CrdtOp (the message module is inside
pmacs-protocol; identity types live at the crate root).

Feature re-added on pmacs-protocol: 'crdt' (was removed in commit 3
as I'd thought CrdtOp was the only feature-gated thing — but
InstanceCapabilities::default and FrontendCapabilities::default both
call cfg!(feature = 'crdt') for their multi_frontend / crdt_replica /
semantic_render defaults). Re-added with a doc comment explaining why.
The parent pmacs crate's 'crdt' feature now activates
'pmacs-protocol/crdt' so the cfg!() check evaluates consistently in
both crates.

Full gate green: fmt, clippy --all-targets -D warnings, lib 1314,
m4_acceptance 83, m8_1/m8_9/m8_10 10/26/19, m9_1 18, m5_8 5,
m11_5_semantic_acceptance --features crdt 2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -72,7 +72,7 @@ lua54 = ["mlua/lua54", "mlua/vendored"]
 # field on the Buffer struct layout, no branch on apply_edit). v1.0
 # builds enable `crdt`; the rope-projection redirect from M10.1 means
 # the feature flip is invisible to v0.1 frontends and to workers.
-crdt = ["dep:loro"]
+crdt = ["dep:loro", "pmacs-protocol/crdt"]
 
 [dependencies]
 crossterm = "0.28"

pmacs-protocol/Cargo.toml

@@ -32,11 +32,15 @@ cast_precision_loss = "allow"
 similar_names = "allow"
 multiple_crate_versions = "allow"
 
-# No features — the wire type set is unconditional. `CrdtOp` is
-# always compiled (matching the original `pmacs::rope::CrdtOp`'s
-# "not `#[cfg]`-gated to avoid feature-flag proliferation through
-# every Edit consumer" decision); the parent `pmacs` crate's `crdt`
-# feature gates loro and op-application, not wire shape.
+[features]
+# Mirrors the parent `pmacs` crate's `crdt` feature. The wire type
+# set is unconditional (`CrdtOp` is always compiled — see
+# `crdt.rs`); the feature exists so `cfg!(feature = "crdt")` checks
+# inside capability-default helpers (`InstanceCapabilities::default`,
+# `FrontendCapabilities::default`) evaluate to the same value here
+# as in the parent crate. The parent activates it via
+# `pmacs-protocol/crdt` from its own `crdt` feature.
+crdt = []
 
 [dependencies]
 serde = { workspace = true }

pmacs-protocol/src/lib.rs

@@ -37,12 +37,18 @@
 pub mod cell;
 pub mod crdt;
 pub mod ids;
+pub mod message;
 
 pub use cell::{
     Attachment, Cell, CellCoord, CellSize, Color, DiffSpan, Glyph, Style, UnderlineStyle,
 };
 pub use crdt::CrdtOp;
 pub use ids::{BufferId, ByteRange, FrontendId, Position};
-
-// The `SemanticFrame` family and the top-level message envelopes
-// follow in the final commit within this PR.
+pub use message::{
+    AdornmentContent, AdornmentPlacement, AttachRequest, BlockAdornment, CursorState, Decoration,
+    DecorationKind, DecorationSegment, FrontendCapabilities, FrontendEvent, GoodbyeReason, Hello,
+    InlineAdornment, InstanceCapabilities, InstanceIdentity, InstanceMessage, InstanceSignal, Key,
+    KeyEvent, Modifiers, MouseButton, MouseEvent, MouseKind, NegotiatedCapabilities,
+    PROTOCOL_VERSION, ResourceBody, SUPPORTED_PROTOCOL_VERSIONS, SelectionSnapshot, StyleSegment,
+    StyleSpan, is_supported_protocol_version, negotiate_capabilities,
+};