remove el_runtime.c — runtime is 100% native El

el_runtime.c and el_runtime.h removed from the active runtime directory
(archived copies remain in el-compiler/runtime/legacy/).
tools/lsp/build.sh removed as it depended on el_runtime.c directly.
AGENTS.md updated to reflect el_seed.c as the sole C dependency.

AGENTS.md

@@ -27,15 +27,17 @@ This is where almost all work belongs. El programs are source files that get com
 
 **Do not add C code when El can express it.** If functionality can be built from existing El primitives (string ops, `exec`, `fs_read/write`, `http_post`, etc.), write it in El.
 
-### Layer 2: The C runtime (`el-compiler/runtime/el_runtime.c`)
+### Layer 2: The C seed (`el-compiler/runtime/el_seed.c`)
 
-This is the hand-written C layer that provides El's native built-in primitives: libcurl HTTP, pthreads server, filesystem I/O, JSON parsing, engram graph store, etc. It is **not generated** — it is maintained by hand.
+This is the self-contained C OS-boundary layer. It provides the `__`-prefixed primitives that compiled El programs call: libcurl HTTP, pthreads, filesystem I/O, arena allocation, etc. It is **not generated** — it is maintained by hand.
 
-**Only edit `el_runtime.c` when you genuinely need OS-level access** (raw sockets, GPU calls, new libcurl features). For everything else, write El.
+The old `el_runtime.c` has been archived to `el-compiler/runtime/legacy/`. The runtime is now native El (`runtime/*.el`). `el_seed.c` replaces `el_runtime.c` as the sole C compilation dependency.
+
+**Only edit `el_seed.c` when you genuinely need OS-level access** (raw sockets, GPU calls, new libcurl features). For everything else, write El.
 
 When you do add a C builtin:
-1. Add the C function to `el_runtime.c`
-2. Declare it in `el_runtime.h`
+1. Add the C function to `el_seed.c`
+2. Declare it in `el_seed.h`
 3. Add it to the `builtin_arity` table in `el-compiler/src/codegen.el` (so the compiler knows the arg count)
 4. Rebuild the elc binary (see below)
 
@@ -50,14 +52,14 @@ cd /Users/will/Development/neuron-technologies/foundation/el
 ./dist/platform/elc elc-cli.el > elc-new.c
 cc -std=c11 -I el-compiler/runtime -lcurl -lpthread \
    -o dist/platform/elc-new \
-   elc-new.c el-compiler/runtime/el_runtime.c
+   elc-new.c el-compiler/runtime/el_seed.c
 # Verify self-hosting:
 ./dist/platform/elc-new elc-cli.el > elc-verify.c
 diff elc-new.c elc-verify.c   # should be identical
 mv dist/platform/elc-new dist/platform/elc
 ```
 
-After changing `el_runtime.c` only (no El source changes), rebuild downstream programs but do NOT need to rebuild the compiler binary itself — the runtime is linked at the application level, not the compiler level.
+After changing `el_seed.c` only (no El source changes), rebuild downstream programs but do NOT need to rebuild the compiler binary itself — the seed is linked at the application level, not the compiler level.
 
 ---
 
@@ -66,7 +68,7 @@ After changing `el_runtime.c` only (no El source changes), rebuild downstream pr
 Each El application has a `build.sh` that:
 1. Concatenates all `.el` source files (stripping `import` lines)
 2. Runs `elc` to produce a `.c` file
-3. Runs `cc` linking against `el_runtime.c`
+3. Runs `cc` linking against `el_seed.c`
 
 Example (cgi-studio daemon):
 ```bash
@@ -102,8 +104,8 @@ Use `exec()` (blocking) or `exec_bg()` (fire-and-forget) with shell scripts to r
 | `el-compiler/src/codegen.el` | Code generator — builtin arity table lives here |
 | `el-compiler/src/lexer.el` | Lexer |
 | `el-compiler/src/parser.el` | Parser |
-| `el-compiler/runtime/el_runtime.c` | Hand-written C runtime (native builtins) |
-| `el-compiler/runtime/el_runtime.h` | Runtime header (C function declarations) |
+| `el-compiler/runtime/el_seed.c` | Self-contained C OS-boundary layer (replaces el_runtime.c) |
+| `el-compiler/runtime/el_seed.h` | Seed header (C function declarations) |
 | `spec/language.md` | Language specification |
 | `BOOTSTRAP.md` | How to recover the compiler from scratch |
 | `elc-cli.el` | Compiler entry point |
@@ -126,4 +128,4 @@ exec("EL_HTTP_TIMEOUT_MS=300000 " + SOME_BIN + " " + args + " 2>&1")
 - New library functions → write in El
 - New OS/hardware primitives → write in C and register in `codegen.el` arity table
 - Never edit `dist/platform/elc` directly — always rebuild from source
-- Never modify `el_runtime.c` to add functionality that El can express
+- Never modify `el_seed.c` to add functionality that El can express