Fix formatter bugs and consolidate snapshot tests

[DaelonSuzuka]

Summary

• Fix grammar tokenization for nested match after : (closes Auto Formatter incorrectly remove space between test value and nested match statement #858) and function calls with spaces before parens (closes A space between method name and arguments causes incorrect tokenization and syntax highlighting #1002)
• Fix unary minus adding space before multi-char identifiers (closes Formatter adds space between minus sign and variable names #865)
• Fix yield(expr) getting extra space before ( — treated like func(, assert(, export(
• Fix signal getting extra keyword spacing inside expressions like yield(signal, ...) — now scope-aware
• Allow any non-negative integer for maxEmptyLines setting (closes Allow Max Empty Lines to be more than just "1" or "2" #1004)
• Fix formatter corrupting git merge conflict markers by splitting <<<<<<</=======/>>>>>>> into separated operators (closes Autoformatter Incorrectly Formats Merge Conflicts #850)
• Fix denseFunctionParameters stripping spaces inside lambda bodies — assignments like x = false inside connect(func(): ...) now preserve spacing (closes Formatting issue of lambda functions #938)
• Scientific notation floats like 1e-6 are already fixed by prior grammar changes; verified with expanded float_notation.gd snapshot tests (closes Formatter adds space inside float literal with negative exponent. #928)
• Convert all formatter snapshot tests from directory pairs to inline format, expand coverage from 35 to 41+ files (55→56+ test cases)
• Add Godot 3 compatibility tests

Grammar fixes (#858, #1002)

• match_keyword and statement_keyword patterns now use (?:^|:) instead of ^\s*, so match is recognized after :
• function_call begin pattern now allows \s* between name and (, so func_name (args) scopes as a function call

Formatter fixes (#858, #865, #928, #938, #850, yield, signal)

• between() in textmate.ts now checks for = before -/+ tokens, treating them as unary when preceded by assignment
• Added yield to no-space-before-paren list (alongside func, assert, export)
• Made signal tokenization scope-aware: keyword in declarations, variable in expressions
• is_merge_conflict_marker() skips lines starting with <<<<<<<, =======, or >>>>>>> entirely, preventing the formatter from corrupting git conflict markers (Autoformatter Incorrectly Formats Merge Conflicts #850)
• inLambdaBody flag on tokens tracks when we're inside a lambda body that's a function call argument — dense parameter formatting is suppressed for lambda body content so assignments keep their spaces (Formatting issue of lambda functions #938)
• Scientific notation 1e-6 is correctly tokenized as a single constant.numeric.float.gdscript token by the grammar — verified, was already fixed (Formatter adds space inside float literal with negative exponent. #928)

Setting enhancement (#1004)

• maxEmptyLines changed from enum ["1","2"] to number with minimum: 0, default 2
• Config value is sanitized: negatives clamped to 0, non-numbers default to 2

Test infrastructure

• All 17 in.gd/out.gd directory pairs converted to single inline .gd files
• Removed the pair-test runner and get_options() helper from formatter.test.ts
• Renamed test.gd → trailing_newlines.gd, merged scientific_notation.gd → float_notation.gd, merged self_keyword_spacing.gd → keywords.gd

New test files for previously uncovered features

• annotations.gd — @export, @onready, @rpc, @warning_ignore, @abstract, stacked annotations
• control_flow.gd — if/elif/else, for..in, while, ternary if, pass/break/continue
• declarations.gd — return types, class_name, extends, signal, static, const
• dense_params.gd — denseFunctionParameters config option, lambda body spacing (Formatting issue of lambda functions #938)
• dictionaries.gd — dict literals, nested/typed dicts, subscript access
• godot3_compat.gd — tool, export, onready, remote/master/puppet keywords, setget syntax, yield()
• is_as_operator.gd — is/is not and as operators
• merge_conflict.gd — git conflict markers left untouched (Autoformatter Incorrectly Formats Merge Conflicts #850)
• method_calls.gd — function call spacing, method chains
• trailing_newlines.gd — strictTrailingNewlines config

Test plan

• All 56+ formatter snapshot test cases pass
• Verify syntax highlighting for nested match and spaced function calls looks correct in VS Code
• Verify maxEmptyLines accepts any non-negative integer in settings
• Verify merge conflict markers are not corrupted by formatting
• Verify lambda body spacing is preserved with denseFunctionParameters: true