mini_parser: trailing whitespace and malformed conditions raise IndexError/KeyError #65

Summary

The condition mini-parser raises unexpected exceptions for several inputs. In particular, adding trailing whitespace to an otherwise valid condition causes an IndexError. A missing closing parenthesis and adjacent operands raise IndexError and KeyError instead of a useful syntax error. These exceptions propagate through AnnotationElementConditionEval(condition=...).

Reproduction

from accvlab.dali_pipeline_framework.internal_helpers.mini_parser import Parser

for condition in ("x = a", "x = a ", "x = a\u3000", "x = (a", "x = a b"):
    try:
        Parser(condition).parse()
        print(repr(condition), "OK")
    except Exception as exc:
        print(repr(condition), type(exc).__name__, str(exc))

Observed at commit 213e5c8:

Expected behavior

Trailing whitespace should not change the result of a valid condition. Malformed conditions should raise a clear ValueError rather than exposing internal IndexError or KeyError exceptions.

Source analysis

• Lexer.next_token() checks for end of input before skipping whitespace, then indexes the input without checking again.
• Parser._parse_prefix() advances past an expected ) without verifying that it exists.
• Parser._curr_token_priority() indexes the priority map with a VARIABLE token when operands are adjacent.

Please add regression coverage for these inputs when fixing the parser.