daemon: rpc/ — Unix-socket transport + generated dispatch wiring (build step 1)

First real code in daemon/. veloxd now listens on
$XDG_RUNTIME_DIR/velox/velox.sock (0600, SO_PEERCRED same-UID check),
frames NDJSON, and routes every method through the generated
velox::proto::dispatch(). The CLI and GUI have a server to talk to.

Modules:
- rpc/ndjson.hpp    — newline-delimited framing, 8 MiB frame cap, CRLF-
                       tolerant, partial-tail buffering. Header-only, tested.
- rpc/event_loop    — single-threaded poll(2) reactor; never blocks the
                       loop. stop()/wake() are async-signal-safe (eventfd).
- rpc/runtime_dir   — $XDG_RUNTIME_DIR/velox resolution, 0700, owner-checked;
                       refuses an insecure fallback rather than using /tmp.
- rpc/uds_server    — listener + non-blocking per-conn read/write with
                       backpressure; handles session.hello (protocol-major
                       check -> -32001, sessionId, transport=uds) and
                       session.subscribe in the server layer; routes the
                       rest through dispatch().
- rpc/dispatcher    — VeloxDispatcher : proto::Dispatcher, all 39 methods.
                       download.list answers an empty table; the rest return
                       "not implemented" (-> -32603) until the store lands.
- main.cpp          — abstract-namespace single-instance lock, signal ->
                       clean shutdown, socket unlinked on exit.

Tests (ASan+UBSan and TSan clean):
- veloxd.ndjson         — framing edge cases
- veloxd.uds_roundtrip  — real socket: hello ok / version mismatch / empty
                          list / -32601 / -32700 / pipelined requests, and a
                          guard on the -32603 collapse documented in P1.

Known gap, filed not worked around: daemon/docs/proto-requests-m1.md P1 —
the generated Dispatcher has no error channel below -32603, so handlers
cannot yet return -32010/-32011/-32013 with their data payloads. The
server layer handles -32001/-32002/-32003 around dispatch(); genuine
in-handler errors collapse to -32603 until PROTO gives handlers a real
error return. Three error fixtures are non-conformant until then.

Not in this drop: rpc/ws_server (next; needs the store for hashed pairing
tokens), store/, sched/, cli/. WS reuses this event loop.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Upd9WhG9oppieig5nRDLig

daemon/CMakeLists.txt

@@ -0,0 +1,41 @@
+# daemon/ produces the veloxd binary and the veloxd_rpc static library it is built from.
+# Owned by lane DAEMON. Wired in by PKG via add_subdirectory(daemon) in the root file,
+# guarded on this file existing.
+#
+# Layering (CLAUDE.md §3): depends on velox::core and velox::proto. No Qt. The engine
+# (velox::core) is not linked yet — it arrives when sched/ and the task glue land; this
+# first drop is the RPC transport + dispatcher skeleton so the CLI and GUI have a real
+# server to talk to.
+
+if(NOT TARGET nlohmann_json::nlohmann_json)
+    find_package(nlohmann_json 3.11 REQUIRED)
+endif()
+find_package(Threads REQUIRED)
+
+# --- veloxd_rpc — the server library ----------------------------------------------------
+add_library(veloxd_rpc STATIC
+    src/rpc/runtime_dir.cpp
+    src/rpc/event_loop.cpp
+    src/rpc/uds_server.cpp
+    src/rpc/dispatcher.cpp
+)
+add_library(velox::daemon_rpc ALIAS veloxd_rpc)
+
+target_include_directories(veloxd_rpc
+    PUBLIC  ${CMAKE_CURRENT_SOURCE_DIR}/src
+)
+target_compile_features(veloxd_rpc PUBLIC cxx_std_23)
+target_compile_options(veloxd_rpc PRIVATE -Wall -Wextra -Wpedantic -Werror)
+target_link_libraries(veloxd_rpc
+    PUBLIC  velox::proto nlohmann_json::nlohmann_json Threads::Threads
+)
+
+# --- veloxd — the daemon binary -------------------------------------------------------
+add_executable(veloxd src/main.cpp)
+target_compile_features(veloxd PRIVATE cxx_std_23)
+target_compile_options(veloxd PRIVATE -Wall -Wextra -Wpedantic -Werror)
+target_link_libraries(veloxd PRIVATE veloxd_rpc)
+
+if(VELOX_BUILD_TESTS AND EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/tests/CMakeLists.txt)
+    add_subdirectory(tests)
+endif()