env: centralize daemon env management; add /mcp slash command to s/sh

- Bump core and 9p submodules for env refactor
- s/sh: export daemon env from $MOUNT/env on startup
- s/sh: add /mcp command

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

9p

@@ -1 +1 @@
-Subproject commit 237e4dec8cdea67535cf5266d4d67b39b8ae37a7
+Subproject commit eef8ccecd93aa4c5a0ec604257cb22d3eaef68eb

core

@@ -1 +1 @@
-Subproject commit 2695567aa4354e71f9d25d17019a83e6f6d1f539
+Subproject commit 44bff71a65da2b5703b10c70d122c30c67c53115

scripts/s/sh

@@ -58,6 +58,7 @@ Input at the prompt:
   /backend [name]   get or set backend
   /models           list available models
   /backends         list available backends
+  /mcp              list MCP servers
   /usage            show token usage
   /ctxsz            show context size
   /q <text>         enqueue prompt for later
@@ -144,6 +145,11 @@ fi
 S=$MOUNT/s/$id
 chat_off=$(wc -c < "$S/chat" 2>/dev/null || echo 0)
 
+# Export daemon environment to this shell.
+while IFS='=' read -r k v; do
+    [ -n "$k" ] && export "$k=$v"
+done < "$MOUNT/env" 2>/dev/null || true
+
 trap '
     [ "$(tr -d "[:space:]" < "$S/state" 2>/dev/null)" = "idle" ] && exit
     printf "\n" >&2; printf "stop\n" > "$S/ctl"
@@ -176,6 +182,7 @@ while true; do
         /backends) cat "$MOUNT/backends" 2>/dev/null; continue ;;
         /usage)   cat "$S/usage"   2>/dev/null; continue ;;
         /ctxsz)   cat "$S/ctxsz"  2>/dev/null; continue ;;
+        /mcp)     cat "$S/mcp"    2>/dev/null; continue ;;
         "/q "*)   printf '%s\n' "${input#/q }" > "$S/enqueue"
                   printf 'queued\n' >&2; continue ;;
         /*)       printf 'unknown command: %s\n' "${input%% *}" >&2; continue ;;