[P2] Reject unknown /workflow run flags before -- delimiter

[brAperia2025]

Context: CodeRabbit feedback on upstream PR coleam00#1875 surfaced a fail-fast parser issue in our fork.

Problem:

• packages/core/src/handlers/command-handler.ts treats unknown tokens starting with -- as workflow message text while still parsing command options.
• Typos like --resume-runid silently disable intended behavior.

Impact:

• P2/P3. Operator mistakes are hidden and can lead to wrong workflow behavior.

Acceptance criteria:

• While parsing command options before --, reject unknown --flags with a clear error.
• Preserve the ability to pass arbitrary workflow message args after --.
• Add tests for typo rejection and post-delimiter literal args.

Reference:

• CodeRabbit comment: Merge AISRV Archon state model into dev coleam00/Archon#1875 (comment)