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",