feat(http-transport): replace tiny_http with axum/SSE Streamable HTTP (#227)

Cargo.toml

@@ -77,6 +77,7 @@ agentmesh = "=4.0.0"
 agentmesh-mcp = "=4.0.0"
 beankeeper = { git = "https://github.com/PromptExecution/beankeeper-b00t.git", branch = "feat/serde-feature", features = ["serde"] }
 ofx-rs = "0.2"
+lazily = { version = "0.59", features = ["statechart", "thread-safe"] }
 
 [workspace.lints.rust]
 unsafe_code = "deny"

crates/ledgerr-mcp/Cargo.toml

@@ -38,15 +38,18 @@ tokio = { workspace = true }
 
 # plugin_info — always available (cross-platform system metadata)
 sysinfo = { version = "0.33", default-features = false, features = ["system"] }
+lazily = { workspace = true }
 
 # self-update feature deps — only compiled when the feature is active
 reqwest = { version = "0.12", features = ["blocking", "json", "rustls-tls"], default-features = false, optional = true }
 semver = { version = "1", optional = true }
 
-# http-transport feature dep — minimal synchronous HTTP server, matches the
-# existing sync dispatch model (no tokio runtime pulled into the request
-# path). See src/bin/ledgerr-mcp-server.rs's serve_http().
-tiny_http = { version = "0.12", optional = true }
+# http-transport feature deps — axum-based Streamable HTTP + SSE transport.
+# tiny_http is removed; axum + tokio-stream replace it. Tokio is already a
+# workspace dep (for budget_reconcile); these add the router and stream
+# adapter needed for SSE server-initiated notifications (issue #227).
+axum = { version = "0.8", optional = true }
+tokio-stream = { version = "0.1", features = ["sync"], optional = true }
 
 # winreg — Windows-only, safe registry wrapper; gated at the cfg level in code
 [target.'cfg(windows)'.dependencies]
@@ -76,7 +79,7 @@ self-update = ["dep:reqwest", "dep:semver"]
 # stdio transport (never replaces it — see infrastructure#139/#141 for the
 # Azure Container Apps scale-to-zero deployment this exists for). Off by
 # default: opt in with --features http-transport.
-http-transport = ["dep:tiny_http"]
+http-transport = ["dep:axum", "dep:tokio-stream"]
 
 # Legacy: gates the old mcp_adapter.rs dispatch and the pre-actor server
 # match-statement path.  The new actor/gate channel system is the default;
@@ -87,6 +90,8 @@ legacy = ["core"]
 [dev-dependencies]
 tempfile = "3"
 calamine = "0.34"
+# Required for axum transport integration tests (ServiceExt::oneshot)
+tower = { version = "0.5", features = ["util"] }
 
 # Enable the b00t feature for tests that exercise McpProvider infrastructure
 # and register_default_providers graceful-degradation coverage.