Document line-significance limitations in the Pico-8 Lua grammar

PICO-8's shorthand `if (cond) stmt [else stmt]` is line-bounded, but
tree-sitter has no built-in newline awareness. Without an external
scanner ( the same mechanism tree-sitter-python uses for INDENT /
DEDENT / NEWLINE ), the grammar greedily binds `else` to the nearest
`if` and takes only one consequence statement for the shorthand body.
Token classification is unaffected, so syntax highlighting renders
identically to a correct parse; only auto-indent and semantic
selection are subtly off, in a code pattern that is uncommon in real
PICO-8 code.

New `grammars/pico-8-lua/KNOWN_LIMITATIONS.md` walks through both
incorrect cases ( the dangling-else mis-bind and the multi-statement
shorthand body ), tabulates which Zed features are and aren't
affected, and sketches the fix. README cross-links it from the
"Known limitations" block and adds it as a prerequisite to the v0.3
LSP work.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -53,6 +53,20 @@ their PICO-8 work continue to get standard Lua treatment.
 
 ### Known limitations
 
+- **Line-significant dialect features are not modeled.** PICO-8's
+  shorthand `if (cond) stmt [else stmt]` is line-bounded — a
+  later-line `else` belongs to an enclosing standard `if`, not the
+  shorthand. Without an external scanner, the grammar can't see
+  newlines, so it greedily binds `else` to the nearest `if` ( the
+  C / Java convention ) and treats a multi-statement single-line
+  shorthand body as one statement plus a sequence of unconditional
+  follow-ups. The parse is structurally wrong but **tokens still
+  classify correctly**, so syntax highlighting renders identically
+  to a correct parse; only auto-indent and semantic selection are
+  subtly affected. Full write-up:
+  [`grammars/pico-8-lua/KNOWN_LIMITATIONS.md`](grammars/pico-8-lua/KNOWN_LIMITATIONS.md).
+  Slated for v0.3 work alongside LSP integration ( which needs a
+  correct AST ).
 - **No language server.** No completion, hover docs, or diagnostics for
   PICO-8 builtins yet — only a static `function.builtin` highlight on
   recognized names. See Roadmap.
@@ -163,7 +177,13 @@ fallback `unknown_section` rule.
 
 ### v0.3 — Language server integration
 
-Wire up [`japhib/pico8-ls`](https://github.com/japhib/pico8-ls) ( or whichever
+Prerequisite: an external scanner for `tree-sitter-pico8-lua` so the
+shorthand-if and shorthand-while bodies are line-bounded the way PICO-8
+defines them. See [`grammars/pico-8-lua/KNOWN_LIMITATIONS.md`](grammars/pico-8-lua/KNOWN_LIMITATIONS.md).
+LSP features that walk the AST ( unreachable-code lint, goto-definition
+through a conditional branch ) need correct structure.
+
+Then wire up [`japhib/pico8-ls`](https://github.com/japhib/pico8-ls) ( or whichever
 PICO-8 LSP is most maintained at the time ) for:
 
 - Completion of PICO-8 builtins ( `spr`, `circfill`, `btn`, `flr`, … ).