Finch 2.4.0: methods, maps, errors as values; str() of any value; macOS and ARM64 docs; Kate support

- fn Struct.method(...) with self by reference, also on C structs
- map[K]V: insertion-ordered hash maps, literals, m[k] += 1, has/get/remove/keys/values
- -> T! / -> !, return error(...), or <value>, or { err }, try; fallible int/float/read_file/write_file/delete_file
- for i, x in list / for k, v in map
- print and str() share one text formatter
- LSP: method and map completion, method signatures; grammar and snippets for VS Code and Kate
- tests: 74 (methods, errors, maps + 11 failure cases); docs at all three levels, en and pl

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

editors/vscode/test/grammar.js

@@ -20,6 +20,12 @@ const code = [
   '    p := Point(x: 1)',
   '    return a + p.x',
   '}',
+  'fn Point.move(int dx) -> int! {',
+  '    map[str]int m',
+  '    n := try parse(s) or 0',
+  '    self.x += dx',
+  '    return error("no")',
+  '}',
 ];
 const expect = [  // [line, token text, scope that must be present]
   [0, 'import', 'keyword.control.import'], [0, '"stdio.h"', 'string.quoted.double'],
@@ -32,6 +38,11 @@ const expect = [  // [line, token text, scope that must be present]
   [7, 'c', 'string.quoted.single'], [7, '3.5', 'constant.numeric.float'], [7, 'true', 'constant.language'], [7, 'null', 'constant.language'],
   [8, 'Point', 'entity.name.type'],
   [9, 'return', 'keyword.control'],
+  [11, 'Point', 'entity.name.type'], [11, 'move', 'entity.name.function'], [11, '!', 'keyword.operator'],
+  [12, 'map', 'storage.type.primitive'],
+  [13, 'try', 'keyword.control'], [13, 'or', 'keyword.control'],
+  [14, 'self', 'variable.language.self'],
+  [15, 'error', 'support.function.builtin'],
 ];
 registry.loadGrammar('source.finch').then((g) => {
   let state = vsctm.INITIAL, toks = [];