fix: treat bare bool flags as true

[ChenJesse]

Summary

• Bare boolean flags like --dry-run (without =true) are now treated as true
• Previously, --dry-run was silently ignored because the flag parser only populated the FlagArg when a value was provided via = (e.g. --dry-run=true)
• This matches standard CLI conventions where passing a boolean flag without a value means "enable it"

Test plan

• Updated existing test case for bare bool flags
• All TestParseTaskOptionsListToMap subtests pass

🤖 Generated with Claude Code

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