BugFix: Reference counting for comma-separated rung instruction arguments

[johnpuksta]

Problem

When a rung contains instructions with multiple comma-separated arguments (e.g., MOV(Source, Dest) or TON(Timer, Preset, Accum)), only the first argument is recognized as a tag reference. Arguments after commas are silently dropped.

Root Cause

Instruction.ParseArguments() splits instruction text by comma but doesn't trim whitespace from the results. For MOV(Source, Dest), the split produces ["Source", " Dest"]. The leading space on " Dest" causes TagName.IsTag() to fail (the base name regex ^[A-Za-z_][\w:]{0,39}$ rejects leading spaces), so the argument is classified as Unknown instead of Reference.

Fix

• Instruction.ParseArguments(): Add .Trim() to comma-split argument results
• ArgumentType.Of(): Trim before type classification (defensive, for direct callers)

Tests Added

• RungTests: Parameterized tests for multi-arg instructions, duplicate tags across instructions, and branch scenarios
• ArgumentTests: Leading whitespace tolerance
• ArgumentTypeTests: Leading whitespace tolerance
• TagNameTests: IsTag() behavior with whitespace (enforces that trimming is not it's responsibility)
• InstructionTests: Comma-separated args with whitespace
• L5XReferencesTests: End-to-end reference counting for same tag in different instructions and same instruction