feat(jobs): real OS threads - Job.parallel_for, fn name, thread-safe Sync

- `fn name` names a top-level function as a value (E_FNREF, lowers to @fn_<name>); the worker
  entry point for Job.parallel_for, which checks it takes (int, pointer-like) and returns void.
- runtime/native/threads.ll (pthreads) and threads_win.ll (Win32 SRWLOCK/CONDITION_VARIABLE): a
  pool of one worker per core but one, parked between batches; every thread claims chunks by
  compare-and-swap. Linked only into programs that use Job/Promise/Sync, by `ludicc -o`,
  `ludic build` and the test suite's build helper.
- Sync.* is real: native mutexes, atomics as cmpxchg retry loops (neither clang takes atomicrw,
  the PC's rejects seq_consistent), mutex-guarded channels, Sync.cpu_count from the OS.
- spawn/despawn on a pool thread stop the program with a located panic.
- examples/library/threads.ludic and its test; docs for fn, Job.parallel_for, Job.is_worker.
- Reseeded (bootstrap-cfree: out.ll == seed.ll). 141/141 on macOS; jobs, threads and the guard
  pass on Windows from the reseeded Windows seed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/editors/shared/ludic.tmLanguage.json

@@ -184,7 +184,7 @@
         { "name": "keyword.operator.logical.ludic", "match": "\\b(and|or|not)\\b" },
         { "name": "keyword.other.clause.ludic", "match": "\\b(phase|query|on|cancellable|public|layer|start|shows|lasts|loads|then|export|internal)\\b" },
         { "name": "keyword.other.ludic", "match": "\\b(import|extern)\\b" },
-        { "name": "storage.type.ludic", "match": "\\b(program|property|model|prefab|namespace|enum|ui|const|var|let|function|handler|entry|event|scene|state|test)\\b" },
+        { "name": "storage.type.ludic", "match": "\\b(program|property|model|prefab|namespace|enum|ui|const|var|let|function|fn|handler|entry|event|scene|state|test)\\b" },
         { "name": "support.type.primitive.ludic", "match": "\\b(int|long|fixed|countdown|bool|entity|string|pointer|byte|words|fixeds|pointers|Vector|IVec2|Rect|void)\\b" },
         { "name": "constant.language.boolean.ludic", "match": "\\b(true|false|null)\\b" },
         { "name": "constant.language.phase.ludic", "match": "\\b(Start|Input|FixedUpdate|Update|LateUpdate|Render|Overlay)\\b" }

tools/editors/vscode/syntaxes/ludic.tmLanguage.json

@@ -184,7 +184,7 @@
         { "name": "keyword.operator.logical.ludic", "match": "\\b(and|or|not)\\b" },
         { "name": "keyword.other.clause.ludic", "match": "\\b(phase|query|on|cancellable|public|layer|start|shows|lasts|loads|then|export|internal)\\b" },
         { "name": "keyword.other.ludic", "match": "\\b(import|extern)\\b" },
-        { "name": "storage.type.ludic", "match": "\\b(program|property|model|prefab|namespace|enum|ui|const|var|let|function|handler|entry|event|scene|state|test)\\b" },
+        { "name": "storage.type.ludic", "match": "\\b(program|property|model|prefab|namespace|enum|ui|const|var|let|function|fn|handler|entry|event|scene|state|test)\\b" },
         { "name": "support.type.primitive.ludic", "match": "\\b(int|long|fixed|countdown|bool|entity|string|pointer|byte|words|fixeds|pointers|Vector|IVec2|Rect|void)\\b" },
         { "name": "constant.language.boolean.ludic", "match": "\\b(true|false|null)\\b" },
         { "name": "constant.language.phase.ludic", "match": "\\b(Start|Input|FixedUpdate|Update|LateUpdate|Render|Overlay)\\b" }

tools/ludic-cli/build.ludic

@@ -48,7 +48,7 @@ function compile_app(src: pointer, out: pointer, mode: int, save: bool) -> bool
 
   if mode == 2 {
     if not shq(`{ludicc()} --headless {src} --emit-llvm -o {ll}`) { return false }
-    if not shq(`{cc()} -O2 {ll}{gl_link_flags(ll)}{vk_link_flags(ll)}{http_link_flags(ll)}{pbf} -o {out}`) { return false }
+    if not shq(`{cc()} -O2 {ll}{gl_link_flags(ll)}{vk_link_flags(ll)}{http_link_flags(ll)}{threads_link_flags(ll)}{pbf} -o {out}`) { return false }
     if not save { shell(`rm -f {ll}`) }
     return true
   }
@@ -58,7 +58,7 @@ function compile_app(src: pointer, out: pointer, mode: int, save: bool) -> bool
   # canonical `ludicc -o` path links it only when Audio.* is used.
   let cocoa = `{home}runtime/native/cocoa.ll`
   let audio = `{home}runtime/native/audio.ll`
-  if not shq(`{cc()} -O2 {ll} {cocoa} {audio} -framework Cocoa -Wl,-needed_framework,GameController -Wl,-needed_framework,AVFoundation -Wl,-rpath,@loader_path{gl_link_flags(ll)}{vk_link_flags(ll)}{http_link_flags(ll)}{pbf} -o {out}`) { return false }
+  if not shq(`{cc()} -O2 {ll} {cocoa} {audio} -framework Cocoa -Wl,-needed_framework,GameController -Wl,-needed_framework,AVFoundation -Wl,-rpath,@loader_path{gl_link_flags(ll)}{vk_link_flags(ll)}{http_link_flags(ll)}{threads_link_flags(ll)}{pbf} -o {out}`) { return false }
   if not save { shell(`rm -f {ll}`) }
   return true
 }
@@ -91,6 +91,14 @@ function http_link_flags(ll: pointer) -> pointer {
   return ` {ludic_home()}runtime/native/http.ll -Wl,-needed_framework,Foundation`
 }
 
+# A program that uses Job.* / Promise.* / Sync.* calls the thr_* OS-thread runtime; link
+# threads.ll only then, as `ludicc -o` does.
+function threads_link_flags(ll: pointer) -> pointer {
+  if not shq(`grep -q "call .*@thr_" {ll}`) { return "" }
+  if host_windows() { return ` {ludic_home()}runtime/native/threads_win.ll` }
+  return ` {ludic_home()}runtime/native/threads.ll`
+}
+
 # the directory part of a path, without the trailing '/' ("" when there is none)
 function dir_of_path(p: pointer) -> pointer {
   var last = -1

tools/ludic-cli/selfhost.ludic

@@ -125,7 +125,7 @@ function cmd_sh_compile(shbin: pointer, in: pointer, outbin: pointer) -> int {
 function game_build_ok(shbin: pointer, game: pointer, outbin: pointer) -> bool {
   let ll = `{outbin}.ll`
   if not shq(`{shbin} {game} > {ll} 2>{tmp_dir()}/gb.err`) { return false }
-  if not shq(`{cc()} -O2 {ll} -o {outbin} 2>{tmp_dir()}/gb.err`) { return false }
+  if not shq(`{cc()} -O2 {ll}{threads_link_flags(ll)} -o {outbin} 2>{tmp_dir()}/gb.err`) { return false }
   shell(`rm -f {ll}`)
   return true
 }

tools/ludic-cli/test.ludic

@@ -578,6 +578,7 @@ function cmd_dev_test() -> int {
   feat_case("library/containers", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14", "containers.ludic (Dict string-keyed hash map + Set string set)")
   feat_case("library/numeric", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20", "numeric.ludic (Huge idle big-numbers + Angle wrapping radians + Percent clamped [0,1])")
   feat_case("library/jobs", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31", "jobs.ludic (Job background compute/defer/fulfill/cancel + Promise all/race/progress + Sync mutex/atomic/channel; issue #14)")
+  feat_case("library/threads", "", "1 2 3 4 5 6 7", "threads.ludic (Job.parallel_for on OS threads + Sync atomic/mutex shared across workers + fn name worker entry)")
   feat_case("library/optionresult", "", "1 2 3 4 5 6 7 8 9 10 11 12", "optionresult.ludic (option some/none + result ok/err/try safety types)")
   feat_case("library/regex", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18", "regex.ludic (Regex match/find/groups/classes/quantifiers/replace + linear-time safety)")
   feat_case("library/grid", "", "1 2 3 4 5 6 7 8 9 10 11 12 13", "grid.ludic (Grid line/flood/line_of_sight + A* pathfinding over the tilemap)")