Interactive key confirmation (`--ask`)

Status: shipped for cleanup (batch + per-key). Other commands remain optional follow-ups.

Shipped behavior (`cleanup`)

Flag	Effect
`--ask`	TTY only: after computing candidate removals, prompt per top-level namespace (segment before first `.`). Global `--yes` skips all prompts.
`--ask-per-key`	With `--ask`: one confirm per key (can be noisy).
Global `--yes`	Overrides `--ask` — full candidate list is removed without interactive prompts.

Ignored when:

--check-only or --json (no interactive prompts).
Not a TTY — --ask is ignored (info log); use --yes or bulk confirm as today.

Implementation

packages/cli/src/core/ask/removal.ts — groupKeysByTopSegment, promptApprovedRemovalKeys.
packages/cli/src/commands/cleanup/index.ts — wires flags after safeToRemove is computed.

Follow-ups (not required to close sprint)

fill / locales delete: opt-in --ask using the same helpers.
Config key reference.commands.cleanup.askGroupBy if we need finer grouping than top segment.

Phase — i18nprune.dev + docs.i18nprune.dev Phase: Key reference unification, preserve module, and regex documentation