feat(#2659): serve hive-matrix-mcp over persistent streamable-http, drop stdio bridge

docs/persistence.md

@@ -234,7 +234,7 @@ Under `/var/lib/hyperhive/agents/<name>/`:
     hourly and deletes terminal task trios older than 48 hours;
     non-terminal (still-running) tasks are never deleted by vacuum.
   - `hyperhive-todos.sqlite` — loose-ends-v2 todo store. In-container
-    MCP daemons (`hive-bash-daemon`, `hive-matrix-mcp`) and `forge_notify`
+    MCP daemons (`hive-bash-daemon`, `hive-matrix-daemon`) and `forge_notify`
     upsert keyed todos here over the harness's in-agent socket
     (`HIVE_AGENT_SOCKET`); the harness merges them into `get_loose_ends`
     output and clears a row on `mark_todo_done`. Replaced the old
@@ -400,18 +400,13 @@ the body + marker check at that point.
 ## Matrix per-agent daemon + token-arrival trigger
 
 `hive-matrix-daemon` is a long-running matrix-sdk Client + sync
-process per agent. Holds the unix socket the stdio
-`hive-matrix-mcp` bridge talks to, emits hyperhive wake signals
+process per agent. Serves its MCP tools directly over
+streamable-http (`hyperhive.mcp.matrixHttpPort`, no stdio bridge —
+same shape as `hive-bash-daemon`), emits hyperhive wake signals
 on incoming room events via `/run/hive/mcp.sock`. Conditional on
 `hyperhive.matrix.enable` (which both the daemon AND the
 auto-injected `extraMcpServers.matrix` entry read).
 
-Socket path lives inside the systemd-managed runtime dir
-(`RuntimeDirectory = "hive-matrix"` → `/run/hive-matrix/`, owned by
-the agent user) so the daemon can bind without needing root over
-`/run/` itself. Both daemon + bridge agree on the path via the
-`HIVE_MATRIX_SOCKET` env var.
-
 **First-boot ordering**: hive-c0re provisions the matrix token AFTER
 agent containers come up. Without the path-trigger sibling
 (`systemd.paths.hive-matrix-daemon`, `PathExistsGlob =

docs/tools/matrix.md

@@ -3,8 +3,9 @@
 ## Built-in matrix MCP (`mcp__matrix__*`)
 
 When `hyperhive.matrix.enable = true` and the host-level matrix
-tuwunel is configured, the harness auto-injects `hive-matrix-mcp` as
-a second stdio MCP server. Tools land as `mcp__matrix__<name>`:
+tuwunel is configured, the harness auto-injects `hive-matrix-daemon`'s
+streamable-http endpoint as a second MCP server (no stdio bridge —
+see Architecture below). Tools land as `mcp__matrix__<name>`:
 
 ### Messaging
 
@@ -68,11 +69,18 @@ room you haven't read yet.
 
 ## Architecture
 
-The daemon (`hive-matrix-daemon`) holds the long-running matrix-sdk
-`Client` + sync loop; the stdio bridge (`hive-matrix-mcp`) is spawned
-per turn and forwards tool calls over `/run/hive-matrix.sock`. Both
-silently exit when `<state>/matrix-token` is absent (account not yet
-provisioned).
+`hive-matrix-daemon` is a single long-running process (one per agent
+container, systemd service in `nix/agent-modules/matrix.nix`) — no
+stdio bridge, no separate bin. It owns the matrix-sdk `Client` + sync
+loop per configured account **and** serves the matrix tool surface
+directly over streamable-http on `hyperhive.mcp.matrixHttpPort`
+(declared in `hyperhive.extraMcpServers.matrix` as
+`{ type = "http"; url = ...; }`). Same shape as `hive-bash-daemon` and
+the built-in `hyperhive` surface (`hive-mcp-http`) — claude reconnects
+to the stable URL every turn instead of respawning a stdio child.
+Silently exits when `<state>/matrix-token` is absent (account not yet
+provisioned); the `systemd.paths.hive-matrix-daemon` watcher restarts
+it the moment hive-c0re provisions the token.
 
 Incoming room events wake the agent via `AgentRequest::Wake` with
 `from: "matrix"`. The wake body format depends on the unread state:
@@ -107,8 +115,11 @@ provisioning flow, and federation config.
 ## Extra MCP servers (per-agent)
 
 Each agent's NixOS config can declare additional MCP servers via
-`hyperhive.extraMcpServers.<key> = { command, args, env,
-allowedTools }`. The module writes the map to
+`hyperhive.extraMcpServers.<key> = { type, command, args, env, url,
+allowedTools }` — `type = "stdio"` (the default, uses `command`/`args`/
+`env`) or `type = "http"` (uses `url`, a long-lived streamable-http
+endpoint — see `hive-bash-daemon` and `hive-matrix-daemon` above for
+the `"http"` shape). The module writes the map to
 `/etc/hyperhive/extra-mcp.json`; the harness reads it at boot and
 merges every entry into `--mcp-config` (under `mcpServers.<key>`)
 and `--allowedTools` (as `mcp__<key>__<pattern>`).