test: cover lexer errors and token display

[omsherikar]

Bring src/arx/lexer.py to full line coverage: Token, TokenList, LexerError, docstrings, escapes, and numeric edge cases.

Solves #41

[Copilot]

Pull request overview

This PR expands tests/test_lexer.py to drive src/arx/lexer.py toward full line coverage by exercising previously untested branches and error paths (Token/TokenList helpers, LexerError formatting, docstring parsing, numeric edge cases, and string/char literal escapes).

Changes:

• Add unit tests for Token.__hash__, Token.get_display_value(), and TokenList iteration behavior.
• Add unit tests validating LexerError message formatting and location propagation.
• Add lexer tests for false, and/or operators, lone . handling, multiple-decimal rejection, docstring delimiter/termination cases, and quoted literal escape/error cases.

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[Copilot]

test_lexer_string_escape_sequences builds the input string with too many backslashes (e.g., \\n/\\t and the ...\\\"end... segment). With the current lexer escape handling, this will not produce a newline/tab and will likely terminate the string before end, causing the assertion to fail. Update the test input so the buffer contains the intended source text: \n and \t (single backslash escapes) and \\\" (a literal backslash followed by an escaped quote), and end the buffer with a real newline (\n) rather than a literal backslash-n sequence.

Suggested change

	ArxIO.string_to_buffer('"line\\n\\t\\\\\\"end"\n')
	ArxIO.string_to_buffer('"line\n\t\\\"end"\n')

[xmnlab]

Thanks @omsherikar