build(mcp): pull in the HTTP/stdio transport features (T10.4)

rmcp gains transport-streamable-http-server + transport-io (the actual
serving code -- the base "server" feature only got tool routing) plus
client + transport-streamable-http-client-reqwest, used solely by this
crate's own in-process MCP-client tests (WA never opens an outbound MCP
connection at runtime, so this is not new egress, FR-MCP-7). hyper/
hyper-util/http-body-util/http/bytes/tower-service are the low-level glue
to run HTTP/1 over a loopback TcpListener in front of rmcp's
StreamableHttpService (a bare tower_service::Service, not an axum app).
All are already in Cargo.lock transitively via reqwest/tauri -- no new
crates, just promoted to direct deps under the existing `mcp` feature.

src-tauri/Cargo.toml

@@ -47,7 +47,25 @@ chacha20poly1305 = "0.10"
 getrandom = "0.2"
 zeroize = "1"                                               # wipe key material from memory on lock
 keyring = { version = "3", optional = true, features = ["windows-native"] }  # OS credential store (sync + AI creds); windows-native = real Credential Manager (else keyring 3.x uses a no-op mock store)
-rmcp = { version = "0.16", optional = true, features = ["server"] }  # MCP server (ADR-0011)
+# MCP server (ADR-0011). `client`/`transport-streamable-http-client-reqwest`
+# are only ever constructed by this crate's own in-process tests (an actual
+# MCP client talking to our loopback server) -- WA never opens an outbound
+# MCP connection at runtime, so this adds no egress (FR-MCP-7).
+rmcp = { version = "0.16", optional = true, features = [
+    "server", "transport-streamable-http-server", "transport-io",
+    "client", "transport-streamable-http-client-reqwest",
+] }
+# Low-level HTTP glue for the Streamable HTTP transport: `rmcp`'s
+# `StreamableHttpService` is a bare `tower_service::Service`, so something has
+# to actually accept TCP connections and run HTTP/1 on top of it. All four
+# versions are already in Cargo.lock transitively (via reqwest/tauri), so this
+# just promotes them to direct deps -- no new crates.
+hyper = { version = "1", optional = true, features = ["server", "http1"] }
+hyper-util = { version = "0.1", optional = true, features = ["tokio"] }
+http-body-util = { version = "0.1", optional = true }
+http = { version = "1", optional = true }
+bytes = { version = "1", optional = true }
+tower-service = { version = "0.3", optional = true }
 
 # audio / transcription / diarization / calendar are integrated per-phase and are
 # feature-gated so the CPU-only build always compiles (NFR-MNT-4).
@@ -106,7 +124,10 @@ pst = []                        # shells out to readpst (libpst) — no cra
 # Phase 9
 sync = ["dep:keyring"]          # remote upload (WebDAV + OAuth providers)
 # Phase 10
-mcp = ["dep:rmcp", "dep:keyring"]   # WhispAssist as an MCP server + hosted-AI creds
+mcp = [
+    "dep:rmcp", "dep:keyring", "dep:hyper", "dep:hyper-util",
+    "dep:http-body-util", "dep:http", "dep:bytes", "dep:tower-service",
+]   # WhispAssist as an MCP server + hosted-AI creds
 
 [profile.release]
 opt-level = "z"      # optimize for size — keep the binary small (NFR-RES-1)