docs: add Networking section + process/OS builtins (net_send, owner, is_server, serialize/apply, arg, exit, run, getenv, read_char, file_*)

Sourced from the compiler's confirmed builtin set and NETWORKING-DESIGN.md, so
the reference reflects the current language surface. 93 -> 104 symbols.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/language/annotations/_section.md

@@ -1,7 +1,7 @@
 ---
 id: annotations
 title: Annotations
-order: 13
+order: 14
 ---
 
 <code>@Name(...)</code> decorators attach compile-time behavior to a handler, property, or function.

docs/language/builtins/_section.md

@@ -1,7 +1,7 @@
 ---
 id: builtins
 title: Builtin functions
-order: 12
+order: 13
 ---
 
 Global functions available anywhere, beyond the namespaced APIs above.

docs/language/builtins/fn-arg.md

@@ -0,0 +1,12 @@
+---
+id: fn-arg
+name: arg_count / arg
+category: builtins
+kind: builtin
+tokens: arg_count arg
+sig: arg_count() -> int   arg(i) -> str
+tip: The command line; argv[0] is included.
+order: 20
+---
+
+Read the process command line: <code>arg_count()</code> is the number of arguments (including the program name at index 0) and <code>arg(i)</code> returns the <code>i</code>th as a string.

docs/language/builtins/fn-exit.md

@@ -0,0 +1,12 @@
+---
+id: fn-exit
+name: exit
+category: builtins
+kind: builtin
+tokens: exit
+sig: exit(code)
+tip: Exit the process immediately with a status code.
+order: 21
+---
+
+Terminate the process now with the given status code. Unlike <code>quit()</code>, which ends the game loop cleanly after the current frame, <code>exit</code> stops the program at once.

docs/language/builtins/fn-file.md

@@ -0,0 +1,12 @@
+---
+id: fn-file
+name: file_write / file_stdout / file_stderr
+category: builtins
+kind: builtin
+tokens: file_write file_stdout file_stderr
+sig: file_stdout() -> ptr   file_stderr() -> ptr   file_write(handle, buf, len)
+tip: Low-level output handles and raw writing.
+order: 25
+---
+
+<code>file_stdout()</code> and <code>file_stderr()</code> return the standard stream handles; <code>file_write(handle, buf, len)</code> writes <code>len</code> raw bytes to one. Most code uses <code>print</code> instead — these are the primitive underneath.

docs/language/builtins/fn-getenv.md

@@ -0,0 +1,12 @@
+---
+id: fn-getenv
+name: getenv
+category: builtins
+kind: builtin
+tokens: getenv
+sig: getenv(name) -> str
+tip: Read an environment variable.
+order: 23
+---
+
+Return the value of environment variable <code>name</code> (empty when it is unset).

docs/language/builtins/fn-read_char.md

@@ -0,0 +1,12 @@
+---
+id: fn-read_char
+name: read_char
+category: builtins
+kind: builtin
+tokens: read_char
+sig: read_char() -> int
+tip: Read one byte from standard input (-1 at end of input).
+order: 24
+---
+
+Read a single byte from standard input, returning its value or <code>-1</code> at end of input — the basis for headless, pipe-driven runs.

docs/language/builtins/fn-run.md

@@ -0,0 +1,12 @@
+---
+id: fn-run
+name: run
+category: builtins
+kind: builtin
+tokens: run
+sig: run(cmd)
+tip: Run a shell command.
+order: 22
+---
+
+Run <code>cmd</code> as a shell command — handy for build steps and tooling written in Ludic.

docs/language/colors/_section.md

@@ -1,7 +1,7 @@
 ---
 id: colors
 title: Color — the named palette
-order: 9
+order: 10
 ---
 
 <code>Color.Name</code> lowers to a plain <code>0xRRGGBB</code> integer at compile time — no runtime cost, identical to writing the hex by hand, but readable. 221 names are built in; a custom shade is any hex literal or a named <code>const</code>. The full palette:

docs/language/networking/_section.md

@@ -0,0 +1,7 @@
+---
+id: networking
+title: Networking
+order: 9
+---
+
+Multiplayer is a compile-time property of the ECS, not glue you thread by hand. Mark fields <code>@Sync</code> and models <code>@Owned</code>; the compiler generates the replication. These are the low-level primitives beneath that sugar, for when you drive the transport yourself.

docs/language/networking/fn-is_server.md

@@ -0,0 +1,12 @@
+---
+id: fn-is_server
+name: is_server / is_owner / local_id
+category: networking
+kind: builtin
+tokens: is_server is_owner local_id
+sig: is_server() -> bool   is_owner(e) -> bool   local_id() -> int
+tip: Role and identity checks the runtime sets.
+order: 3
+---
+
+The runtime sets the local role. <code>is_server()</code> is the authority check, <code>is_owner(e)</code> is true when this peer owns <code>e</code>, and <code>local_id()</code> is this peer's id. Prefer role annotations to sprinkling these through gameplay code.

docs/language/networking/fn-net_poll.md

@@ -0,0 +1,12 @@
+---
+id: fn-net_poll
+name: net_poll
+category: networking
+kind: builtin
+tokens: net_poll
+sig: net_poll(buf, cap) -> int
+tip: Receive queued bytes from the transport; returns the byte count.
+order: 1
+---
+
+Copy up to <code>cap</code> waiting bytes into <code>buf</code> and return how many arrived (0 when nothing is queued). Pair it with the generated <code>apply</code> to fold an update back into the world.

docs/language/networking/fn-net_send.md

@@ -0,0 +1,12 @@
+---
+id: fn-net_send
+name: net_send
+category: networking
+kind: builtin
+tokens: net_send
+sig: net_send(peer, buf, len)
+tip: Send bytes to a peer over the host's transport.
+order: 0
+---
+
+Send <code>len</code> bytes from <code>buf</code> to <code>peer</code>. The transport itself is a host-provided seam — UDP natively, WebRTC/WebSocket on the web, or a loopback in tests — so the same game runs over any of them.

docs/language/networking/fn-owner.md

@@ -0,0 +1,12 @@
+---
+id: fn-owner
+name: owner / set_owner
+category: networking
+kind: builtin
+tokens: owner set_owner
+sig: owner(e) -> int   set_owner(e, id)
+tip: Read or assign an entity's network owner.
+order: 2
+---
+
+<code>@Owned</code> gives a model an owner slot; <code>owner(e)</code> reads the peer id that owns entity <code>e</code> and <code>set_owner(e, id)</code> assigns it (the authority decides). Ownership gates who may write <code>@Sync(to: owner)</code> fields.

docs/language/networking/fn-serialize.md

@@ -0,0 +1,12 @@
+---
+id: fn-serialize
+name: serialize / apply
+category: networking
+kind: builtin
+tokens: serialize apply
+sig: serialize(e, buf) -> int   apply(e, buf, len)
+tip: Compiler-generated per-model replication of @Sync fields.
+order: 4
+---
+
+Generated from the ECS schema per model: <code>serialize</code> writes an entity's <code>@Sync</code> fields into <code>buf</code> and returns the length; <code>apply</code> folds received bytes back onto an entity. Together they are the replication substrate the sugar builds on.

docs/language/operators/_section.md

@@ -1,7 +1,7 @@
 ---
 id: operators
 title: Operators & tokens
-order: 11
+order: 12
 ---
 
 The symbols the grammar recognizes.

docs/language/types/_section.md

@@ -1,7 +1,7 @@
 ---
 id: types
 title: Types
-order: 10
+order: 11
 ---
 
 Ludic is statically typed; most code uses just <code>int</code>.