feat(redteam): custom target adapter commands (list/get/create/update/delete/validate)

[cdot65]

Summary

Slice 4 of #299: Red Team custom target adapters (SDK 0.16.0), additive to the existing redteam group. Stacked on #305 (pin bump) — independent of the AI Gateway slices.

Changes

• SdkRedTeamService adapter methods: listAdapters/getAdapter/createAdapter/updateAdapter/deleteAdapter/validateAdapter
• Update is read-modify-write: upstream PUT is full-replacement and an omitted variable key is DELETED — the CLI merges overrides onto the current record and resends stored variables (secrets as value: null = keep stored). --variables explicitly replaces the whole set. --prompt required (upstream never stores it)
• Secrets render (redacted) keyed off is_redacted (live tenant masks with '**********', not null)
• Validate: preflights broker channel ONLINE with a clear failure message; auto-fills the required full variables array from --adapter <uuid>; renders the execution outcome with stderr/traceback on failure and exit 1
• --script-file (auto-base64) / --script-b64; --draft saves without running the script
• Docs page docs-site/docs/cli/redteam/adapters.md; changeset (minor)

Testing

• TDD: 9 failing wrapper specs committed first; +9 helper specs (script resolution, variables parsing)
• 885 tests green on this branch; tsc + Biome + docs build clean

Closes #303