feat(errors): recoverable failures as values — try/else over ok/err results (#46)

A fallible function returns a `result` value, built with ok(payload) on success
or err(message) on failure. The caller recovers a value with `try EXPR else {
… }`: on ok the whole expression is the payload; on err the else block runs —
with the failure message bound to `error` — and its trailing expression supplies
the fallback. It is a plain branch on the result's tag: no exceptions, no hidden
control flow, nothing unwinds. is_ok(r) / is_err(r) classify without unwrapping.

Payloads are any i32-width scalar (int/fixed/bool/entity). The feature is
additive and only kicks in when ok/err/try are used, so untouched programs
compile byte-identically (verified) and the C-free bootstrap fixpoint holds.
Complements panic/assert from #8 (the unrecoverable half). The optional
top-level frame `recover` stays deferred (needs a frame-abort mechanism); the
full tagged-union/any generalization is tracked in #1.

Adds the `try` keyword and ok/err/is_ok/is_err builtins across the compiler,
the vocabulary header, JetBrains + TextMate/VSCode grammars, the docs inventory
and pages, examples/library/recover.ludic, and a regression case.

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

tools/editors/jetbrains/src/main/kotlin/io/ludic/ide/LudicTokens.kt

@@ -50,7 +50,7 @@ object LudicVocabulary {
     val STMT = setOf(
         "let", "return", "if", "else", "while", "for", "in", "spawn", "despawn",
         "enable", "disable", "match", "machine", "state", "become", "where",
-        "and", "or", "not", "break", "continue", "new", "emit", "cancel"
+        "and", "or", "not", "break", "continue", "new", "emit", "cancel", "try"
     )
     val PRIMITIVES = setOf("int", "long", "fixed", "bool", "entity", "string", "pointer", "byte", "words", "fixeds", "pointers", "Vector", "void")
     val PHASES = setOf("Start", "Input", "FixedUpdate", "Update", "LateUpdate", "Render")
@@ -65,6 +65,7 @@ object LudicVocabulary {
         "ui_tick", "ui_render", "ui_clicked", "ui_set_text", "ui_set_int", "ui_focus",
         "ui_focused", "ui_visible", "key", "reg", "set_reg", "self", "save", "load",
         "status", "print", "string", "quit", "panic", "assert",
+        "ok", "err", "is_ok", "is_err",
         // compiler intrinsics: the floor the Ludic-written runtime stands on
         "bytes", "words", "resize", "free", "fill",         "arg_count", "arg", "file_stderr", "file_stdout",
         "offset",

tools/editors/shared/ludic.tmLanguage.json

@@ -172,7 +172,7 @@
     },
     "keyword": {
       "patterns": [
-        { "name": "keyword.control.ludic", "match": "\\b(if|else|while|for|in|match|machine|become|return|spawn|despawn|enable|disable|where|break|continue|new)\\b" },
+        { "name": "keyword.control.ludic", "match": "\\b(if|else|while|for|in|match|machine|become|return|spawn|despawn|enable|disable|where|break|continue|new|try)\\b" },
         { "name": "keyword.operator.logical.ludic", "match": "\\b(and|or|not)\\b" },
         { "name": "keyword.other.clause.ludic", "match": "\\b(phase|query|on)\\b" },
         { "name": "keyword.other.ludic", "match": "\\b(import|extern)\\b" },
@@ -204,7 +204,7 @@
         {
           "comment": "the runtime surface — every name here resolves to rt_<name> in runtime/native",
           "name": "support.function.builtin.ludic",
-          "match": "\\b(min|max|abs|clamp|seed|rng_range|rng_chance|fixed|floor|map_size|map_row|tile|clear|present|fill_rect|frame_rect|put_px|text|text_int|font_load|text_ttf|text_w|text_h|image_load|draw_image|draw_image_scaled|draw_9slice|png_load|sprites_load|draw_sprite|draw_sprite_scaled|ui_build|ui_open|ui_tick|ui_render|ui_clicked|ui_set_text|ui_set_int|ui_focus|ui_focused|ui_visible|key|reg|set_reg|self|save|load|status|print|string|quit|panic|assert)\\b(?=\\s*\\()"
+          "match": "\\b(min|max|abs|clamp|seed|rng_range|rng_chance|fixed|floor|map_size|map_row|tile|clear|present|fill_rect|frame_rect|put_px|text|text_int|font_load|text_ttf|text_w|text_h|image_load|draw_image|draw_image_scaled|draw_9slice|png_load|sprites_load|draw_sprite|draw_sprite_scaled|ui_build|ui_open|ui_tick|ui_render|ui_clicked|ui_set_text|ui_set_int|ui_focus|ui_focused|ui_visible|key|reg|set_reg|self|save|load|status|print|string|quit|panic|assert|ok|err|is_ok|is_err)\\b(?=\\s*\\()"
         },
         {
           "comment": "compiler intrinsics — these lower straight to libc or the OS",

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

@@ -172,7 +172,7 @@
     },
     "keyword": {
       "patterns": [
-        { "name": "keyword.control.ludic", "match": "\\b(if|else|while|for|in|match|machine|become|return|spawn|despawn|enable|disable|where|break|continue|new)\\b" },
+        { "name": "keyword.control.ludic", "match": "\\b(if|else|while|for|in|match|machine|become|return|spawn|despawn|enable|disable|where|break|continue|new|try)\\b" },
         { "name": "keyword.operator.logical.ludic", "match": "\\b(and|or|not)\\b" },
         { "name": "keyword.other.clause.ludic", "match": "\\b(phase|query|on)\\b" },
         { "name": "keyword.other.ludic", "match": "\\b(import|extern)\\b" },
@@ -204,7 +204,7 @@
         {
           "comment": "the runtime surface — every name here resolves to rt_<name> in runtime/native",
           "name": "support.function.builtin.ludic",
-          "match": "\\b(min|max|abs|clamp|seed|rng_range|rng_chance|fixed|floor|map_size|map_row|tile|clear|present|fill_rect|frame_rect|put_px|text|text_int|font_load|text_ttf|text_w|text_h|image_load|draw_image|draw_image_scaled|draw_9slice|png_load|sprites_load|draw_sprite|draw_sprite_scaled|ui_build|ui_open|ui_tick|ui_render|ui_clicked|ui_set_text|ui_set_int|ui_focus|ui_focused|ui_visible|key|reg|set_reg|self|save|load|status|print|string|quit|panic|assert)\\b(?=\\s*\\()"
+          "match": "\\b(min|max|abs|clamp|seed|rng_range|rng_chance|fixed|floor|map_size|map_row|tile|clear|present|fill_rect|frame_rect|put_px|text|text_int|font_load|text_ttf|text_w|text_h|image_load|draw_image|draw_image_scaled|draw_9slice|png_load|sprites_load|draw_sprite|draw_sprite_scaled|ui_build|ui_open|ui_tick|ui_render|ui_clicked|ui_set_text|ui_set_int|ui_focus|ui_focused|ui_visible|key|reg|set_reg|self|save|load|status|print|string|quit|panic|assert|ok|err|is_ok|is_err)\\b(?=\\s*\\()"
         },
         {
           "comment": "compiler intrinsics — these lower straight to libc or the OS",