Verbs with CLI-reserved positional-arg meanings (resume, compact, memory,
commit, pr, issue, bughunter) were falling through to Prompt dispatch
when invoked with args, causing users to see 'missing_credentials' errors
instead of guidance that the verb is a slash command.
#160 investigation revealed the underlying design question: which verbs
are 'promptable' (can start a prompt like 'explain this pattern') vs.
'reserved' (have specific CLI meaning like 'resume SESSION_ID')?
This fix implements the reserved-verb classification: at parse time,
intercept reserved verbs with trailing args and emit slash-command guidance
before falling through to Prompt. Promptable verbs (explain, bughunter, clear)
continue to route to Prompt as before.
Helper: is_reserved_semantic_verb() lists the reserved set.
All 181 tests pass (no regressions).
07b7ff55a3