Fix Python translation pipeline: InstanceCall, control flow, and construct support

[joehendrix]

Fix end-to-end translation of target.method(args) instance calls, control flow constructs (return, break/continue, while loops, nested try/except), and 10 previously unsupported Python constructs that caused the pipeline to fail with translation or type errors.

• Emit InstanceCall from PythonToLaurel for target.method(args) patterns and translate through Laurel resolution and Core translator with self-stripping, since PySpec already strips self from method signatures.
• PySpec procedures now declare Any-typed parameters with preconditions (requires Any..isfrom_string(x)), keeping the Core translator language-agnostic.
• Handle void procedures (0 outputs) when their result is assigned to a variable — emit call without assignment target to avoid Core arity mismatch.
• Translate return as Exit "$body" instead of assigning to the first output parameter, which after heap parameterization could clobber $heap. Generate unique labels for nested try/except blocks. Hoist while loop variables to function scope. Translate break/continue via labeled Exit.
• Translate augmented assignment (+=, -=, *=), ** operator, f-strings, ternary expressions, slicing, tuple for-targets, and import tracking. Emit Hole for dict/set comprehensions and generators. Type exception variables as Any.
• Add regression tests exercising the fixes through the dispatch/heap-parameterization path:
  • test_instance_call_result.py — assign result of client.get_item() to a variable and return it (the core InstanceCall bug this PR fixes).
  • test_while_var_scope.py — variables declared inside a while loop body must be accessible after the loop exits; exercises while-loop hoisting.
  • test_augassign.py — augmented assignment (count += 1) after a service call.
  • test_pow_operator.py — ** power operator (base ** exp).
  • test_fstring.py — f-string interpolation (f"{name}_bucket") used as a service call argument.
  • test_ternary.py — ternary/conditional expression ("a" if flag else "b") used as a service call argument.
  • test_slice.py — list slicing (items[1:]) on a service call result.
  • test_tuple_for.py — tuple unpacking in for-loop targets (for k, v in pairs).
  • test_import_usage.py — referencing an imported module (sys.argv[1]) as a service call argument; exercises moduleAliases tracking.
  • test_except_var_usage.py — using the exception variable (as e) inside an except block; exercises exception variable typing.

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