fix(cli): validate issue priorities before credentials

[bdsqqq]

changes

• reject invalid priority strings instead of silently clearing to zero
• accept case-insensitive documented names and exact numeric strings 0–4
• validate before credentials on list/create/update/batch; preserve omission

verification

1,105 offline tests, typechecks, artifact checks and build passed; regeneration deterministic across 205 files. argv-to-real-core/SDK-method payload regressions and independent review pass. no new live calls.

limits

full parity is incomplete; 0104 output contracts and exhaustive coverage/live evidence remain open. stacked on #36; draft only.