feat: Add Matrix messenger support via HTTP API

Implements MatrixCliMessenger using direct Matrix Client-Server API calls.
No external CLI dependency - just REST calls to homeserver endpoints.

Features:
- Password and access token authentication
- Send/receive messages via /sync
- Room alias resolution
- E2EE-compatible (delegates crypto to homeserver)
- Configurable sync timeout and filters

Part of tier 1 CLI-based messenger support (#115)

Author: rexlunae

crates/rustyclaw-core/Cargo.toml

@@ -21,10 +21,11 @@ web-tools = ["dep:scraper", "dep:html2md"]
 browser = ["dep:chromiumoxide"]
 mcp = ["dep:rmcp", "dep:schemars"]
 matrix = ["dep:matrix-sdk"]
+matrix-cli = []  # Matrix CLI messenger using HTTP API (no external deps)
 whatsapp = ["dep:wa-rs", "dep:wa-rs-sqlite-storage", "dep:wa-rs-tokio-transport", "dep:wa-rs-ureq-http"]
 # NOTE: matrix excluded from all-messengers due to matrix-sdk 0.16 recursion limit bug.
 # Use `--features matrix` explicitly if needed.
-all-messengers = ["whatsapp"]
+all-messengers = ["whatsapp", "matrix-cli"]
 full = ["web-tools", "browser", "mcp", "all-messengers"]
 
 [dependencies]